I have a couple pieces of 1" aluminum tubing, that are 12 feet long. $4 each.
They were the center element sections of an old HF beam.
They will go to the scrap yard, with a bunch of other stuff, and worth a couple of $ for scrap value, if nobody wants them.
They are not perfectly straight, but the bends a slight, and very near the end, so at lest 10 feet should be straight.
I probably have other aluminum tubing, if you want something that might telescope into these, to make a longer section.
Rod J