A friend who is into computers made one of his own design. His rig has a back window, and his solution won't work if yours doesn't.
He mounted a mirror above the rear window at a 45-degree angle, then mounted a computer-compatible wi-fi camera on the inside wall, looking up at the mirror. He put his laptop on the dash to receive the camera signal. It works a treat, and you don't even need to correct the video to give a mirror image because the camera is looking into a mirror.
Frank and Eileen
No longer RVers or FR owners