another way to make your own whisker pole
A friend of mine had end fittings like you showed and used 2 pieces of pvc pipe attached in the middle with a threaded piece so it could be broken down for stowing. It did eventually break but he had it for a while, certainly got his money's worth.
Look into scrap metal shops
I've purchased 6061 from a scrap metal shop here locally (in Dallas, TX). Might want to check phone books. Variety varied over time, so if you aren't in a hurry they might keep an eye out for some for you.