In my mobility car my dashcam is plugged into the 12v socket, I haven’t bothered with a rear camera this time.
In my wifes car (not mobility) we just got her a new dashcam (NextBase, can’t remember which one 🤯) which allows a small camera to be plugged into the side of it facing backwards into the vehicle and out the rear window… maybe not as perfect as having one in the rear window but a lot easier to fit and should be good enough to pick up the basics… ie colour, approx speed of other vehicle, direction if they make off 🤞