I have just bought a new head unit, which has rear view camera function, i. e it turns on as soon as the car is in reverse, but no image other than guide lines, what would be the best camera for this with minimal disruption to the bodywork, its an atoto 6 premium. 

Anything off Ali-Express that replaces the tailgate handle or number plate light, they all work great and cost less than €10 delivered, have installed a couple both worked well & were easy to install.

As J.R. says I think they're all much of a muchness due to the fairly low Res TV signal they use.

 

That said I did buy one that professed to use a better quality sensor than the really cheap ones, but I doubt it makes much, if any, difference.

 

https://www.amazon.co.uk/dp/B07MYR8KBJ?ref=pd_basp_dp_primary

 

I'm happy with the one I got, but definitely don't pay any more than that!

The one I currently have has LED's for rear illumination, they are not needed as the camera has excellent low light resolution and even the puny non LED reversing lights are more than enough, if they were I/R leds then I could have reversed in stealth mode but they are normal white light LEDS and were illuminated all the time the camera is powered which means all the time the ignition is on if you take the convenient feed from the rear wiper motor like I usually do.

 

Not good having a very bright white LED light facing the rear when you are driving forwards at night.

 

I cant for the life of me recall how I resolved it, I think there must have been a seperate wire as I did not run another feed from the reversing lights, in any case the LED array is no longer working and the camera works just fine at night.