The cheap ones that are mostly a cable with lens on one end and USB plug in the other just isn't worth the bother. Picture quality is crap.
On one I have I managed to get dirt behind the lens...
Waterproof? My @ss!
(I was checking the drains, not the south side hole of my own body, but you get the idea... )
The current one is from BILTEMA(parts and tools store from Sweden... Yet another store chain out to conquer the world... )
and it has a dedicated screen and a 7.6mm diameter camera.
Here's a similar one, but with 3.9mm camera tip...
https://www.amazon.com/dp/B07TB6JS46/ref=emc_b_5_i
Yeah, $139.
That's not bad, actually, for a camera like that.
In larger diamter (8mm) you can get dual view cameras. Not just a front facing, but a side facing camera as well. Good for checking all kinds of stuff, really.
If you want good quality, you probably have to rent one or hire someone with one, or expect to pay £100 or more.