Im not sure what he uses but I have looked before and I would go with this. Probably the best bang for your buck. You build it yourself but you buy the prints. I think its like $17 for the prints and the materials all depend on how frugal you are.
http://www.gottrikes.com/
Its hard to beat what some companies offer on prebent roll cages though. But if you are like me you would probably want to make your own anyway.