You don't really have to pick up dead animals on the road to get hair for your brushes, although my husband did volunteer to get a skunk tail for me....
Any of the sporting places, like Pro Bass, Cabala's, etc., etc. carries supplies for fly fishing and the guys who tie their own lures. I have ordered Artic Fox, squirrel, and elk, and they have a ton more.
My grandson is also a prime supplier of fur and hairs. He saves tails from deer, squirrel, fox, rabbit, raccoon, and anything else he harvests during hunting season. He saves horse hair from grooming his horse and hair from the bull's tail when he is being groomed for show. He is a really good grandson! (and an excellent hunter)
Oddly enough, the one species that I am coveting and have been unable to find is from a goat. I want some hair from between the shoulder blades of the goat, but I don't know anybody who has goats who will share a bit of hair.
We also have a never ending supply of bamboo for handles. I do mean a NEVER ENDING supply!
I have an abundance of hairs, tails and etc. If you will send your address, I will be happy to share.