surge protection for backup camera

The problem is called 'load dump'.  International and SAE standards define this as a spike of maybe up to 270 volts on the 12 volts system.  But 60 volts is more typical of what 12 devices are designed to withstand. 

 Load dump protection typically comes with a supply for that electronic device.  Protection from load dump is typically part of the circuits that create a stable required voltage from the wildly fluctuating 12 volts.  But that supply must state load dump protection either explicitly or in numbers that state an input voltage of at least 60 volts.

Hooking it up to a backup light does nothing to eliminate load dump damage. Using a switch also does almost nothing.

If its power supply does not state protection from load dump (as defined previously), then you have a serious problem create by the manufacturer who should have including protection in his power supply.  Doing it right inside the supply costs so little. Installing load dump protection for that inferior power supply is expensive. That protection even defined in both SAE J1455 and  ISO 7637-1 standards.