They don't make it very easy. You have to snuffle around the community values, or safety, or selling guidline pages before you find the reporting page. Then you have to pick a reason for reporting someone. For lack of anything closer, I chose "using photos without permission."
The trouble is that eBay can't investigate someone for something that can't be proven. I'm not aware of anything concrete that says the Bulgy fellow's a crook. AFAIK, the only person who has a valid complaint in this whole thing is the seller of the original saw. His photos and writing, his copyright. Email that guy again and let him know someone's lifted his auction.