The unfortunate fact, Tony, is that here in the U.S,
because people are
accustomed to paying <$25 for a case with power supply (250 Watts is the
rating) including shipping, it's hard to get vendors to stock replacement
fans of any sort, let alone good and quiet ones.
Digikey has some nice ones. Big thread a while back in the pro audio
newsgroups about a quiet high quality fan replacements.