If this has happened on a continuous basis, you may be able to get a hold of someone in NYPD and have them talk to him. They may not be able to arrest him or anything of the sort, but a good talking to by a few of the local authorities would definitely wake him up.
I had this same sort of thing happen to me a few years ago, and the guy that ripped me off had also done so on the SRT-4 forums. I had a member from those forums PM me with the guy's name and address which turned out to be real. I had contacted my local authorities with no luck, but on a long shot I called his local authorities who paid a visit and let him know they knew about the situation. I had my money back 10 minutes after they walked out the door.
The entire ordeal took me about 3 weeks to get sorted. BUT, if you're persistent, and maybe if one of the many local guys (or a few of them) who see him daily help, there's at least a chance this can be resolved. Good luck man, I hate Doucher's like these.