To ask where to buy bras for 13yo?

[seriouslynonames]

My Dd13 has long been wearing cheap stretchy crop tops from M&S but I need to get her some bras or something more substantial as the crop tops barely fit now. I had a brief look at M&S 'first bras' selection the other day (she wasn't with me or could have tried some) but they all look a bit rubbish.
Should I just be looking at regular bras? She is quite slim so I don't think most shops will do the low band sizes she would likely need, but maybe I could get stuff online? Or are there other good shops for teen bras? Or I could try sports bras?
Any recommendations welcome please! I feel I ought to know where to go but most shops don't seem to stock smaller sizes.
Do I need to do proper measuring too? I read so many bad review of the M&S measuring service, and different ways to measure etc and being small of bust myself I have just muddled along with whatever seems to vaguely fit over the years.
Thanks for any ideas of where to shop!

These are nice https://direct.asda.com/george/lingerie/bras/padded-comfort-bras-3-pack/G007144317,default,pd.html?redirectFromInt=1&cmpid=ppc--geor-------_-dskwid-s92700073870135760_dm&utm_campaign=pla:Fashion-_Catch_All&utm_source=google&utm_medium=cpc&gad_source=1&gclid=CjwKCAiAkp6tBhB5EiwANTCx1I4CcdMp38j3oqopoJdi35wshPBNPPo39PcIMIwjDl7Ojraeqfn9iBoCkkQQAvD_BwE&gclsrc=aw.ds
You can remove the pads.
H&M have nice ones too. It seems to be more about comfort now. And small, medium etc rather than proper sizing.

My DD won't wear a conventional bra with wires and nylon lace. She doesn't understand how women do it. She only wants crop tops and supportive vests

My DD has the non wired first bras from Asda - for some reason when I try to link the page it comes up as the homepage but they're easy to search on the George website.

You can measure her yourself with the boob or bust method. Since M&S, Primark etc all allow men into the women's changing rooms I will not take her to a shop for a fitting, we just measure at home. DD has sensory issues but finds those comfy.

M&S do some plain t-shirt bras that are fairly soft and comfy and don't show under things like school shirts. I would measure yourself (or get her to do it) using the boob or bust range then take her to try them on. It didn't get mine quite right but it narrowed down the search and I got a better fit than the M&S bra fitting lady gave me. She also insisted that the smooth t-shirt bras just weren't going to fit me right and sold me a lacy number which I wore twice before deciding to do my own shopping!

I bought cheaper bras while DD was still growing. M&S, Next and supermarkets all good. Primark too.
Under school blouses the t-shirt type bra is better and the nude colour shows through less than white.
You might find a wider range of sizes online than in the shops.

John Lewis do supportive crop tops. I wear them and they are so much more comfortable than underwired bras.

I got my daughter properly fitted for bras, she has a very narrow back but very large cup size so important to get correct fit.

I have big boobs but also now prefer non wired crop tops and DD is going the same way. Her first bras were m&s but expensive and not very supportive. She prefers some slightly stretchier ones we got from Sainsbury's

I'm a size 6 on top and have managed to get bras that fit in Asda and Primark. I pretty much ditched under wire bras and only tend to wear them if a particular outfit requires one. I wear padded crop tops for everyday or the non-wired bras. Much comfier.

I'd measure her at home if she's willing using the Boob or Bust calculator. Then you have a decent starting size to look for some comfy, no wired t-shirt bras. Most supermarkets do a decent range as does H&M and Primark

M&S Angel range.

We’re lucky and have a great independent local shop with a lovely woman who put my very reluctant and embarrassed DD at ease and measured her properly (definitely no men around - completely agree re: the problem with M&S.) After needing crop tops from 9 she was into proper bras by 10 and really needed measuring as she was so slim round the back but needed decent support. Shops like that will stock a decent range of kids/teen bras and be able to advise.

Having had a bad experience at m&s, we were in town and looking for somewhere easy and quick.....and ended up in Ann Summers of all places! Walked through the shop very quickly but they were amazing in there, so kind and knowledgeable and she came out with a much better and appropriate size than either I or M&S could sort. Bought 1 plain basic one from there and then sourced plenty in primark for 32 back but larger cup

You really do need to measure her/get her to measure to get a basic idea of where to start. Bras, like most other clothes, do vary in size from style to style and brand to brand, but a rough idea gives a starting point.
My DD was quite happy to measure herself using the boob or bust method on their website.
Depending on what you end up with, the M&S Angel range isn't bad, but does come in strange sizes.
If she has a bigger band measurement their Bodysoft and Flexifit ranges are quite good, only start at a 30"/32", but don't go very big in the cups..
If she has a small band measurement, Boux Avenue are worth a look. They start at a 28", but generally come up a bit small.

Thanks for all the replies! I haven't worn underwired for a good few years now and I think she will be happy with non wired or a better crop top. Although I think she would prefer ones that do up at the back rather than over the head. Will try boob or bust and see what she comes up as and take a look online at the shops suggested. She has a slim back so will probably need to shop around to find what works. My mum never took me bra shopping I just got my sister's cast offs, even if they were the wrong size, until I was able to buy my own!! So I would like to do better than that for DD. Thanks again!

These are similar to the ones I have from Asda. They fasten at the back, give enough support and are very comfy.

https://direct.asda.com/george/lingerie/bras/non-wired-lace-trim-first-bra-2-pack/GEM1026408,default,pd.html?cgid=D27M3G1C1