If you can't find 'em you could always make 'em. Wouldn't be too hard, get some cardboard and make a template off the shape of the door opening. Transfer the pattern shape to plywood and cut. The hinge is pretty simple, you can make a slide window from plexiglass or just have it screwed in and sealed. If you want 'em to look really good buy some fiberglass and resin and wrap 'em in it the paint with textured paint. That way if they look a little wavy you wont see it.