I found this camera for $35 after coupon; http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_2-4-Inch-Wireless-Backup-Camera-System-Peak_6050271-P_N3597A_A|GRP2021____ You have to enter a filler to get it over $60. I used cotter pins. Enter code BIG25 for $25 off. Shipping is $9, but instore pickup is free. It is only 2.4 inch, but it's cheap.
If its too good to be true... I don't know, I find my 7" HU screen just usable in terms of a camera screen. Let us know how it works out.
The only problem I see is that the camera is designed to be connected to the backup lights for power. That way it only comes on when the car is in reverse. But since the license plate is on the hatch and the backup lights are on the body, it might take more work than it is worth to run wires to the backup lights. A search of the site shows some others just connected it to the rear wiper power.
