I can't help you with the door panel but my '76 Argosy came with no keys. I was lucky in finding keys that work amongst my pack rat key collection. Otherwise, you can drill out the locks on the compartments and replace with new locks availble from most hardware stores.
I don't know why folks don't list their location in their profile, but there might be an RV boneyard near you where you could look for the door panel.
May you camp where wind won’t hit you, where snakes won’t bite and bears won’t git you.