My son bought them for me but it was just an inexpensive ebay set. It included two side view cameras, two regular cameras, wiring, and a 7" color monitor. About $200 - 250 and has worked flawlessly for the past 16 months. The monitor modes can show virtually any view or split screen view including all 4 cameras at once. Works great in low light. I'll ask him for link to the vendor.
A rock took out the lens of the bumper mounted camera and he got me a replacement for around $50.
Anyone who has poor visibilty out of their rear view mirror will find that this will totally change your driving experience. The side view cameras were a bit of a pita to wire up and in hindsight I could do w/o them, but they do come in handy occassionaly changing lanes in heavy traffic and backing in tight quarters.