Make your own. Everything else is the music industry is fake. I doubt anyone will tell if you just found some vinyl snakeskin looking materia and covered them. Trust me...no one will know.
BUT...
you might have to head to a womans fabric shop to get it.
If you are dead serious, you should hit up ebay (or the net in general) and look for someone that sells snake skins. YOu could then cover your own headphones with real snake skin. I highly doubt anyone that maufactures headphones uses real snakeskin. It is probably just a pattern...unless someone buys the headphones, covers them, then resells them.