Depending on how old it is, Heartland may be able to sell you a new door. For older ones, you can try Bontrager's. They deal in out of production parts. There's also a RV junk yard in SW Michigan (forgot the name) that might have it.
For mine, I bought the doors similar to mine from another owner that had replaced his OEM swing doors with slam doors he had made. Good thing he saw my posts cuz nobody had them.
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