When you say skin, I guess you mean the outer section that is welded to the door carcass? They come up on eBay very occasionally, for big money. It may be worthwhile buying whole doors too as very often once the skin is removed, the rest of the door carcass can be rotten. You need a good bodyshop to fit a skin well, I've done them myself but it takes lots of patience to ensure that the door will line up properly. There's a pair of rear skins on eBay at the moment.
