I think the aluminum boxes that you would get now from Courtney Berg would come from Cancade. Apparently there is some joint venture, merger, type arrangement between the two companies. It was mentioned at the farm show last year that they were working together. I don't know what the details are though, didn't ask to many questions about that, had other issues to chat with them about.
A friend and fellow firefighter is a stainless and aluminum welder/fabricator, he has helped me come up with some fantastic solutions for customers. He and I have often talked about building grain boxes and trailers, he does beautiful work, but ramping up production to allow for economy of scale is a challenge. Ironically I read this post this morning and thought again about our half-baked ideas....and then he stopped in again this afternoon, so I showed him this post and talked a little more. Even to just build a small handful of units....
ITB from Coldale, AB used to build a really nice aluminum box. There were a few around and they stood up really well. I haven’t seen a new one for years so I expect they don’t make them any more but might be worth a call
ITB still builds Aluminum boxes in outside of Conrad, Montana. The dealer is 3V Distributing from Conrad. I have bought two boxes from them the first one lasted us 22 years with no issues other then tires separating and bending up some sills. When we got the last one about 5 years ago we put fenders on the truck which I hope will save the box in the event a tire lets go. Would go again if we needed another box.