Surely one camera will assist with reversing and also offer rear view.  I see no necessity for two cameras?
		
		
	 
One is narrow angle (60⁰) for rear view function and the other 120⁰ to give a wide view close up. Trying to do both functions with one camera is a compromise that simply doesn't work. (I tried it with a cheap reversing camera many years ago, the rearward view was totally valueless)
The company I linked to sell 
Twin camera s in a single housing, that's what is probably going onto the back of my PVC. So my existing (rearview 60⁰) camera, wireless transmitter and receiver are on the market if anyone is interested. I am keeping the monitor as that will work with a twin camera system (I have checked with tge company)