Currently it's illegal to sell real tortoise shell of any sort. However I have heard of folks buying antique combs, compacts and jewelery made from tortoise sheel and turning those into picks.

I heard a story that Tony Rice wandered into a music store in Paris a few years back and found a whole stash of real picks that the owner sold him dirt cheap. Like several dozen for about ten bucks. That may be just an inernet rumor though.