Ralph, What you are describing is a metal roof. In older mobile homes, where this roof was used, there was no decking and a large roll of metal was unrolled over the house. It was fastened at on end and then stretched from the other. When stretched, the second end is fastened down and then the sides are folded over, caulked and stapled.
I have no idea where you would find a replacement except to look up mobile home manufacturers and inquire with them. I don't believe this method of construction is common today in "premanufactured homes". The other possibility would be to go directly to sheet metal suppliers and find out if they can provide what your need.