On Monday, April 29, 2019 at 6:31:00 AM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
I am not a qualified mechanical engineer to tell you it would carry the load but I would think that you could buy what you need at any steel supply house knowing the length and width/height plus, importantly, the wall thickness. Best of luck, John (OHM)

A piece of cake, really. If you don't happen to have metal working and welding equipment, any good shop should be able to put it together. A galvanizing place may be harder to find. If you prime and paint instead, suggest etching the steel with dilute phosphoric acid before painting. Jasco Metal Prep is available at many hardware stores or paint supply places. Paint it on, hose it off.