You may be able to order a door from Winnebago that would cover the hole. I'd measure the hole and call them.
You also could look inside the pantry and see if you have a finished shelf that matches that could be a cover for the hole.
You could even make your own door and cover it with carpet, fabric or vinyl.
I robbed a door from the cabinet above the side window and I mounted a TV in front of that side cabinet. The door fit right over where the old TV was mounted and we use the area for storage.