I use:
http://www.amazon.com/Cooler-Master-Hyper-Plus-RR-B10-212P-G1/dp/B002G1YPH0/ref=sr_1_2?s=electronics&ie=UTF8&qid=1387503481&sr=1-2&keywords=Cooler+Master+Hyper+212


If you don'y mind spending more:

http://www.amazon.com/ARCTIC-Accelero-Mono-Plus-Cooler/dp/B006DAD8HS/ref=sr_1_6?ie=UTF8&qid=1387502864&sr=8-6&keywords=arctic+cooling+accelero

I think MrTeal is using them in the pic on the first page and I've seem pics of other people using them as well.