I used the fan off of a Thermaltake TR2-R1 CPU cooler. It's pretty quiet, but you won't be able to fit the aluminum case on your miner! I just left the bottom piece covering the board (and of course necessary for protecting the ASIC board) attached and screwed on the cooler! It fit right into the 3-pin fan connector on the board but you will have to take the heatsink off. I recommend also using new thermal paste such as Arctic Silver 5.

To be honest, any 92mm computer fan will cool those 30w ASIC boards down to just a few degrees over room temp with minimal noise. If you go low profile, you can use the aluminum case!

MOSFET heatsinks may also help keep the thing cool, even if you don't overclock. All of these items are extremely cheap on Newegg, TigerDirect and Amazon, or at your local electronics store.