I too was looking for a backup camera.
I was backing out of my garage and forgot my car was in the driveway. I wasn't looking and was looking on my phone to close the garage door, and almost sideswiped the car.
I bought this the other day at Costco.
It works great and totally wireless and the camera is solar powered (also can USB charge it) the monitor has to be plugged into cigarette lighter, just have to find a place to mount the screen. It comes with a mount but I want a clean look and don't want to start putting suction cups on the windshield.
https://www.costco.com/type-s-6.8-wide-screen-solar-powered-hd-wireless-backup-camera.product.100504814.html