I don't know of any sites of where you can find non-nylon collars but perhaps checking with a local pet supply store...not a chain store and see if they have any options from their suppliers to order something in from you. I'm sure they must be available. Or perhaps taking some materials to a seamstress or tailor shop and getting one made. I know a few people have made them on here before.
I would try a leather collar from a farm supply or a pet store. We have a Shaka collar for Donner and it has a cloth type material sewed on the inside so the nylon doesn't come into contact with the dog.
I wondered the same thing when Logan starting loosing hair on his ears, but he was wearing a leather collar with an occasional nylon PATRIOTS one on game day!
Good luck and my only advise with the leather is because it is a natural material they tend to want to eat it, we take off all collars in the house and Logan jumped up and grab his one day to try have a tasty snack.
Ashley has a Lupine collar ( given to her by her buddy the Vet..he's really sweet on Boxers!)
Funny thing was she HAD a nylon collar, and walking her was a chore, because she would sit down every few feet..and scratch like crazy at it..I thought it was because she is not collared in the house ( due to rough play with the cats, and my fear of her becoming entagled when she chases them UNDER things). But I put the Lupine collar on her..she has never scratched again. Good thing too is they are gaurenteed for life..if anything breaks or wears out..you mail it back..they send you a new one for free. I checked pricing on them..and a 14-22" adjustible was only like 10 dollars here..and they snap on..God I hated trying to buckle the collar on a less than 4 month old wiggle worm!! ( She knows collartime means she's going somewhere..and gets kinda excited! )