I would rather spend my money on camping fees, fuel, or other needs rather than a backup camera for a trailer. There has never been a single time that I have found one to be necessary or even desirable.
I suggest that the OP try towing and using his trailer for a bit of time before spending the money on one. I think he may find it entirely unnecessary.
Just make sure you have good towing mirrors and use them. When backing into a campsite, get out and look before backing, plan your approach, and use a spotter (wife or other) to warn of problems and when to stop.
I always had my wife stand right where I wanted the rear left corner of my trailer to end up. I could then aim at her and usually backed in in one shot. She would raise her arm up when the corner reacher her location.
Barney