FWIW, I've used this product, which is now $59 for screen and camera:
Amazon.com: PYLE PLCM35 3.5-Inch TFT LCD Monitor/Night Vision Rear View Camera: Electronics: Reviews, Prices & more
I don't recommend it for replacing a side mirror, because glare disables the product too often, and the screen isn't bright enough to read out of the corner of your eye. It would be fine for a back-up camera, because you can afford to take a second to squint at the screen, or you could mount it someplace relatively dark.
It does have a great field of view and adequate picture quality, though.