Anyone have a U.S. source for this U channel stock? Closest I have found so far is .875 x .875 bar, then turning 61% of it into chips. Even .875 x .875 x .125 wall square tube would be great - I can easily cut one side out to yield U channel.

I have bought most of my tube from Tube Service in Phoenix, AZ, and some other "odd" sizes (where I didn't need 12-foot lengths) from onlinemetals.com. So I've been sourcing metal for a while - rather than just pointing me to a bunch of places to check - a pointer to someplace that definitely has either the U channel or the square tube would help a lot. Need 6061-T6, not the 6063 architectural stuff.