Best endoscopic camera to use?

Looking to buy an endoscopic camera to check for skips (Someone who vacated without paying but did not remove lock)
I used to be able to just shake the lock but with these Janus doors I cant hear any echo with the empty units I tested.
Basically im going to take the snake camera and feed it over the rollup door to check inside.
Anyone else done this? If so what model/brand did you have luck with.