Not sure if this is against ebay rules, but could you start some auctions for handlebars or other knock off items that basically warn people of the fakes? Even if you listed as set of bars for retail or above, but at the top of the description put in the notice about the fakes. I'm guessing anyone laying down that much coin for some bars isn't going to only read the 'cheap' ebay listing so maybe they will be warned. That would suck to have your bars fall apart underneath you. Good luck resolving this!

Edit: I just remebered seeing a show on cnbc a few weeks ago about how some big nat'l chains are trying to get ebays help in shutting down auctions with obviously stolen merchandise. Items, like generators, that are for sale for less than HD and others pay for them and HD is the only one that sells some of the items. The end result is that ebay is being very uncooperative so the retailers are doing their own research / investigations to shut these people down.