Look up Refund Management Services, they run commercials here in Calgary, apparently this is exactly the type of issue they deal with. According to the commercial they say they only get paid on positive results. I have no personal experience with them so I don't know if they're any good or not but it sounds like the type of thing you're looking for.
I just googled them and found this link
http://www.refundmanagement.com/aboutus.asp
Good luck.