I haven't constructed one yet, but my plan is to use an inexpensive camera from a racing drone (~$15 from china)hooked up to a drone battery. The signal will go to a receiver I already have, which I will mount in the truck. This is only for backing up and wont be in place while traveling. If you are electronically inclined, cobbling up something could be fairly inexpensive.
camera that I have (there are MANY others): Caddx.us Bettle V1 L FPV Camera for RC Hobby DIY FPV Racing Drone Quadcopter (those are search terms on the bay- idk, but I bet I'm not allowed to post the direct link. I have no interest in these financially).
