I got single pieces from a local home depot, 8' lengths off the shelf. Anyway, all these suppliers use a small set of dies to form flat rolls of painted metal into the corrugated stuff so maybe only a 1/2 dozen styles.
You can remove the screws and just lay new panels over the old if you don't want to mess with removal.
EDIT: Oops! Just realized you have three minor ribs between the peaks. Still could work if the edge profiles are the same, but you'd have to remove the two originals. Anyway, you should be able to take you photo and ask some of the building supply places if they can find it.
