Here's a link for what you're looking for.
2 NICE Papst Muffin Type Fans 120V - eBay (item 270201838748 end time Jan-14-08 18:28:05 PST)
You can also find aquarium-type fans which are essentially the same thing. If noise is going to be a problem check the decibals before you buy. If the seller doesn't mention the noise level, it's probably loud.