Unless this person has put more than a few hours of work into a prop or something time-consuming, they most likely don't know how valuable it is to the creator. If he does, then he cares as much for the creator as a common internet pirate, in which case far fewer methods of stopping him will work.
I'm trying to test some... computer things using his email reply, but I still need to check if he replied at all.
I say send him a legitimate-looking C&D from "Microsoft", just so he'll stop the BS and go home and everyone can get some rest.
EDIT: And does eBay take down auctions/sales for recasted items? I didn't know they did, but it'd help. A lot.