WCIII for PSX is rather easy to find. I'd suggest hitting Half.com before Ebay. Half has a good tendency to be looked over, and then you find copies of End Run for $6.
Most major European countires have their own eBay and Yahoo auction sites, which should be able to help you out. I've got a load of stuff from http://list.auctions.yahoo.com/uk which seems to be the best for the UK stuff.