Tori, the BC8 and BC14 have 50mm fans while the BC29 has 60mm fans. You can get 50mm fans, though, at either source listed above. The BC8 fan is 15mm "thick" and you can get fans for as little as $2 each at Newegg. (See this link for 50mm fans at NewEgg:
Newegg.com - Computer Parts, PC Components, Laptop Computers, Digital Cameras and more!) Spec-wise, they're noisier than the SilenX fans. You also need to know in advance that you'll have to do a 4- or 3- to 2-wire conversion which is easy to do, actually (you just use the yellow and the black wires, which are 12V and Ground, respectively). Nanotuners also has stock fans that should work and they'll be happy to tell you what you need for the replacement.
By the way, I got my SilenX fans installed this weekend. They're very quiet and I'm happy not to be hearing the rattling from those cheap fans that Oceanic uses. They are thicker, however - 25 mm (1-inch) - a full 10mm thicker than the stock fans. No problem, though - it will fit the case. The stock screws won't work as they're too short. Instead, make a quick trip to the hardware store and pick up some #6 x 1-1/4 sheet metal screws and drill out the plastic posts in the cover with a bit that is appropriately sized to avoid breaking the plastic. The SilenX fans come with a 3-wire connector and a 4- to 3-wire adapter. I spliced the 2-wire leads from the old, stock fans onto the 4- to 3-wire adapter to make a 2- to 3-wire adapter to power the fan. Quick and easy work - about 30 minutes, max - to a quieter BioCube 29.
