Extra soft school shirts

[Severalreasons]

My son who's started secondary school this morning has been crying that hos school shirt was uncomfortable, he's fine with almost all other clothing but hates shirts.
Any ideas where I can get some that are extra soft or any tips to make it more comfortable for him please?

I think M&S and Asda do sensory friendly ones

I bought 95% cotton shirts in Next , for a girl but I would assume they do boys. In her case it was because she’s prone to overheat. I thought they might be too soft for the tie to sit right under the collar but they’re fine. They feel lovely.

I see Marks do a cotton one too but no idea how it feels.
but this is the Next one 97% cotton it is.
https://www.next.co.uk/g224138s5/461161#461161

DS who has a lot of sensory issues wears a thin cotton t-shirt under his. I think these are them: www.marksandspencer.com/4-pack-pure-cotton-vests-2-16-years-/p/clp60292755#intid=pid_pg1pip7g2r2c2

He's a bit hot with them this week, but loathes the shirts even more!

Thank you I'll have a look at all the links.
I've seen some sensory ones but they seem to have the rip things on them rather than buttons which I know he wouldn't like. He doesn't have issues with buttons but is just super uncomfortable.
It's weird because he used to as a toddler have issues with certain pieces of clothing but then has seemed fine for the past however many years and now it's started again. He was almost on tears. I'm wondering if it could just be that he's in a new school and not doing well with the change in things that's manifesting as this?