I have no knowledge of this sort of thing, so the only way I can see it working (sorry, but I'm not very imaginative) is for you to order a bespoke service - probably easier if you live in a large city, or near quaint coastal villages. Obviously you could use the Internet yourself (but then so could your prospective clients), but if you could track down a mixture of sellers on something like Etsy - I got some things from an Etsy artist that were lovely, and very good value, who I first found out about on here - and also from some little shops that sell well made products, that are not easily found on the high street. You could also visit some National Trust shops, museum shops, etc.
However, you would need the capital for the initial layout, as not only would you need to have some photos of potential packages, including what you are sending things in, eg strong, pretty cardboard boxes (all eco materials hopegully), or wicker baskets etc.
You would also need some photos of a selection of some lovely, good quality, but not too expensive, products - a few examples being things like a genuine Scottish tartan scarf, made out of lovely soft wool, but probably not cashmere, or, I have a pair of earings and a pendant, that I bought from a shop in Pitlochry, that are made of compressed heather, in I think metal (maybe silver) and glass capsules - I haven't found them yet since moving, and my memory is not the best. However, it must be at least 8 years since I bought them, so I don't even know if the shop is still there, or what their prices are like now, but I thought they were very reasonable at the time.
Other things that are small and good value, can be semi-precious stones, some of which people say have healing properties for different things - I bought a small one for one of my adult children when they broke a bone, and the bone ortho was genuinely surprised at how quickly the bone had healed (he didn't know about the stone). Most people will probably consider that a coincidence, or the placebo effect, which might not be quite so easy with broken bones, but who knows!
Anyway, another idea is a wooden love spoon from Wales, they are cheap, but as part of a package for a newly engaged couple, they could be considered a bit of fun, and don't take up much space on a kitchen wall, or shelf - or the bedroom, of course.
I think it is a very good idea to enclose some foodie treats as well, I am rather fond of some of the products found on Fortnum and Mason's website, and although maybe not particularly good value, something like a pot of jam from there, or a tube of biscuits in a nice tin, to go with other things in the parcel might just be a little bit different to a jam from Tiptree (as nice as they are!).
Of course you could get all those sort of things together, and then unfortunately not get any takers, but I suppose most new ventures take at least some capital, and probably quite a bit of risk - but then a few make millions. I'm not sure that this is in that category, but I can think of one woman who started a small business selling party things, and she has done quite well for herself, and her daughters even better (depending on your values of course). Sadly for him, her son's personalised marshmallow business didn't turn out quite so well for him, but he seems to have married quite well too, which is maybe what mum wanted for her loved ones! Actually I think that they seem a lovely family, and I think the eldest daughter and her family is particularly lovely.
Sorry, to have waffled on, maybe I could be your source finder in chief? 😂