I see no downside for you here. You knew they were fakes, and therefore paid a price you were willing to pay. It is not illegal for you to own them, just for you to sell them.
You're not going to be able to wipe the seller from the face of the Earth unless they're within the US. I'm guessing they're not. If they are, let me know and we'll....induce a little regret on his part. I don't sense you're morally able to propagate the problem by ever selling them, so enjoy your hole-fillers and just don't patronize the seller in the future.
You could always come up with a stamp of your own if it's that bothersome.
Edit to add: Was all your communication with the seller within the Ebay system? If so, even with an overseas seller you can file a "Substantially Not As Described" complaint against the seller, not so much to recover your money as to make him go away. The Feds would nail Ebay to the wall if they knew Ebay was willingly allowing the sale of non-stamped replicas....another consideration is that, effective February 20th, replica coin sales are banned from Ebay.
The best thing about a bicycle is that it uses no gasoline, therefore the chance of fiery death is greatly reduced.
Catman, Gary Burke, Bigg Fredd, coinguybrian, numismo, Johnny54321 - CCF members emeritus, now part of Heaven's Own Coin Club.Our members sell on eBay!