Another option is to make your own using the cutout as the new door.
The framing on the inside can be made of wood, but I like aluminum better. A good source for almost free aluminum is your local Goodwill or St. Vincent or recycling store. They often have used aluminum screen doors for a couple of bucks.
These have all sorts of interesting extrusions, hinges, locks and fasteners that can be used for a project of this sort. The aluminum is easy to work and is strong and light weight