You can get the pipe from an industrial plumbing supply house. They may have a scrap piece around that they will sell you cheap -- they may even give it to you. Also, if there is a big building project around (like building an apartment complex) stop in and say "Hi" to the foreman and ask him if he thinks he'll have anything left over for you to have. NOTE: a 12 pack will usually get you what you want.
Once you get the pipe, spend the $ to get pipe caps to seal up the tube. You can configure them all kinds of ways to fit/lock the pipe.
Oh yes, that pipe is heavy so take a friend and rope when you go get it.
Steve