When i wanted a metal roof for my BR last year I could not find one anywhere and the ones made out of fiberglass or plastic or whatever they are were just too expensive and was not what I wanted. Personally, I went to a local Metal store and bought a 4' x 8' sheet of alum diamond plate. It cost around $150. From there I took a large piece of cardboard and cut & chaped it to my specs. Since I was going to have a lot of diamond plate left over, I also made an upper stereo console to mount on the underside. this was also made from cardboard templates. The metal worker charged me $100 to cut and weld the roof and the console. I drilled the holes and mounted and wired everything. Still with a lot of left over diamond plate, I started to cut pieces with jig saw and installed in various places (see my pics). Ran out of ideas and still have some left.
Just an idea.