Long time ago, Amazon was a treasure trove for those of us who provided HONEST reviews in exchange for products. Amazon put a stop to that, but back then, one of the items I scored was an endoscope camera. I used it a few of times so I could review it, but it has sat on a shelf since. Enter OctoPrint / OctoPi. Turns out, this camera works perfectly with OctoPrint - just follow the directions on - https://github.com/foosel/OctoPrint/wiki/Webcams-known-to-work.
The problem, though, was how to mount the camera. Ten minutes in Sketchup and thirty minutes print time, yielded me with a suitable mount. The camera is a snug fit at a 22.5° angle and there is a guide on the rear to prevent the mount from pivoting. The mount is secured to the rail slightly above the build plate using a 4mm screw and a t-nut.
The built-in LED lights of the endoscope are not a sufficient enough light source to adequately light the build plate, so you'll also need to install some sort of lighting fixture.
-=[ EDIT ]=-
Apparently, somehow, this model wasn't watertight. I swear I thought it was. Anyway, I have uploaded the corrected version.