They stopped production. I was in the same boat as you--looking for a 128MB 9100 (Visiontek is the name I came up with) and I was unable to find one anywhere that was being sold as new. When people say "They're around, you just have to look" I have to think that they haven't actually looked themselves. Because I looked--and I'll bet you have too--and I could not find a new one ANYwhere. Just listings that said "Out fo Stock/Discontinued" etc...
I ended up buying one on eBay last night. Cost me $90, and I thought that was fine. It's the best PCI card out there as far as I could tell, so I'm happy. Keep checking eBay; I'm afraid that's the only advice I can give you.
Good Luck!