This one seems quite good:

http://www.ebay.com/itm/Apple-G5-AGP-ATI-Radeon-9600-XT-128MB-Mac-version-free-shipping-/290925989859?pt=DE_Elektronik_Computer_Computer_Graphikkarten&hash=item43bc8a4fe3

It's a good price considering that shipping is free within the EU. Ask the seller if it's a real mac card and not a flashed one just to make sure. If it's a real mac card, go for it.