Well, Mullet. Just this evening, I ordered a pound of horsehair from a horsehair dealer, naturally. This is for horsehair rope for my siege engines, but who knows what else I can do with it. About 30 bucks per pound, but you can order half pounds.
How about human hair? I found some global trading sites that you can contact Asian human hair dealers from. Not sure what to think of that yet. Macabre, maybe? Were the donors living or dead? In antiquity, the best engine ropes were supposedly made from women's hair.