I bought and installed a wired rear view camera on my shuttle bus. It was low cost - around $59.
AliExpress.com they sell all kinds of stuff. I have bought several flashlights, LED panels for replacing my most used interior lights, ect.
Put in the search line wireless back up camera, and then search by price. You will find hundreds of results. I have tried a 'security camera' but it does not work well. When you look behind the RV, the drivers side will be on the right side of the screen, not the left, like when looking in a rear view mirror, so while possible, it is much better to use a back up camera.
Good luck,
Fred.