You could check out the Inland Metals scrapyard on 1st Ave N in between Park and McDonald St..The aluminum stuff is in the south east corner and they get a lot of new and used industrial scrap metal so you may find something and the price wil be right.I picked up a whole pile of 2.5" stainless with nice bends in it for about $25 on time and a floor jack for $3 that had a broken wheel.