2004 Coachmen Cross Country water fill control panel

If you get to the back of the panel, I think you'll see they're pretty standard plastic ball valves for PEX plumbing. On my Coachmen ('98 Santara) there's an access panel over the back that can be removed with a few screws.

If you can remove one of the other knobs, you could take it to a hardware store and look for one with a similar mount.