Loose Ends has a variety of bamboo... but it can get expensive. If you got a couple pieces they should last you a very long time, or you could go in on some with someone. Also, you can find lots of bamboo that grows in North America now. I know there are several places around me that have some large patches of it.
I used bamboo as part of my waterfall all i did was go to like the local garden and craft place (not a big place like Home Depot) and look for the bsmboo poles for holding up plants. They came in a variety of sizes from like 1 1/2 to like 1/2 and all u have to do is cut the tube to size.