Superflow MV-50 Air Compressor fitting

[65convertible]

I have a Superflow MV-50 12 volt air compressor. The female quick release coupling has gone bad is leaking air. A small o-ring has come loose and there seems to be no way to get it back into position. I cannot, so far, get a reply from the Mfg.

Anybody have an idea how to repair this? What coupling to get? A decent replacement compressor?

Thanks