when I was in TX, we used to make them out of 24 and 36" oil pipe. I hadone that was 7' long. The oil pipe was pretty readily available down there and worked better than anything else I've ever used. If you can find some locally, that's what I would recommend using.
There is a guy around the corner from my house that makes them...allways has a few diffrent models out in front of his house..smokers etc.. give me a idea what your looking for ill go see how much...or stop by and we will cruise over and chat with him.