I use to get all kinds of steel and aluminum at a scrap/ pipe place in either Norwalk or Santa Fe. I think there name is Patterson or Peterson something like that .
I do remember they are on Firestone east of Norwalk Blvd. But look at your local industrial scrap yard they will sell at a per lbs. price instead by the ft.
I just built a bed rack with hoist and ramps to pull my quad up into a Stepside made it out of 1/ 1/2", 1 1/4", 1" and 1/2" sq. tube.
Steel price was about $60.00 and aluminum for the ramps was $40.00 same ramps are $250 on line.