Hello there, the box I used is a Cantex 8x8x4 that I got at Home Depot. Interestingly enough, I cannot find them on their site anymore, exactly, but this is very close. May just be an old picture.
http://www.homedepot.com/p/Carlon-8-in-x-4-in-Junction-Box-E989N-CAR/100404099
Let me know if...