Last year I picked up a Good Sam (Rand McNally) 7735 GPS. It has a 7" screen. I knew it had a video input but never got around to using it until recently. Thought I would list what I bought to add a rear view camera to it. I know it would be more convenient to have a permanent mount, but I don't want another camera sitting out in the elements 24x7 and eventually losing its seal, so I used the large suction mount I wasn't using that came with my GPS. I added a safety strap in case it lost its grip but so far some very rough roads haven't made it come loose. It is mounted to my trailer's rear window.
Good Sam - Rand McNally 7735 GPS (Camping World)
20FT GPS Camera Video Cable 2.5mm Aux to RCA AV-IN Adapter (Amazon) https://wheelstips.com/best-rear-view-camera
Pioneer Backup Camera ND-BC8 (Best Buy)
10' RCA video cable (Best Buy)
The Pioneer camera came with 33' of cable that reaches up to the hitch area. The GPS video adapter cable has 20' of cable that reaches from my truck's dash to the hitch. Then the 10' RCA cable is used to connect those 2 cables together when hitched.