Amazone and Harbor Fright have several low end borescope / endoscopes that are semi-useful to check engine internal conditions and lost parts.
One of the cheapest is about 16$ , and it is small 5.5mm w/6 little led lights USB and says waterproof . (search amazon for : GCA 5.5mm Diameter USB Waterproof 6 Led Endoscope ....etc) There are some little 7mm endoscopes for 13.73$ , and I think there are some smaller ones in the 2mm size. They are cheap , fun, not professional quality.
The cheaper borescopes NEED some way to view their little camera so you MUST connect their long cable to a some sort of laptop/notebook/smartphone to view the picture. Their little LED lights aren't too bright, but OK if you know what your looking for.
The next jump up increase in price is the "wireless" endoscope , borescope, snake camera that connects to a smartphone or computer /viewer easier and has a more rigid bendable cable (versus looses wire cable). They start in the 30-40$ price range. They often have more LED lights to see with.
Then there is the Harbor Fright Digital Inspection Camera style (about 74$ retail ) that has a built in viewer in a pistol grip style.
There are many many many other makes of various quality and prices as the electronics for them little cameras have gotten very inexpensive in the last 3 years..
Finally, a lot of the bore-scope, endoscope, snake cameras have little mirrors or magnets that attach to the camera end to give you another side viewing angle or ability to grab iron bits ... BUT watch that you attach them firmly (even Elmers glue them on) cause if that mirror/magnet catches on something and falls off ; then you have another thing to worry about.
