i'm not a regular e-bay user so i'm not sure if you could do this, but could you open up a spoof e-bay account (using a new anonymous hotmail a/c) used purely to put negative comments on a.holes accounts in the event of them ripping you off? bit like having a spoof facebook account to send msgs to people when you want to remain anonymous...?
obviously you wouldn't put negative comments with any reference to the transaction in question which would make it obvious who you really are..? and you'd leave it a week or two..
either that, or find out where they live and hit them hard with a crank extractor in a sock....... good luck mate, hope it works out