Where to got captured door panel nuts

[demian5]

On my 70 passenger, 2 of the 4 captured nuts that the lower door panel screes thread into, are gone. not in the bottom of the door. And a 3rd one I have to put tape on to keep from falling into the door when I remove and install the door panel.

I believe they are just wedged in there and not welded. Over time, the metal in the door changes shape and not longer holds them.

Where can I get replacements?

Thanks in advance.