My borescope was an Ebay purchase, but I don't remember the brand name offhand. It plugs into the USB port on my laptop and projects its image onto the monitor. I did a little shopping for the smallest possible diameter of lens (5 MM) so I could inspect chambers and barrels of small bore rifles. A somewhat larger lens would probably give a sharper focus for engine inspections if you don't need to access very small holes. There's a wide variety of choices and prices, and like anything else, "Ya gets what ya pays for!"
When the borescope and the headspace gauges come out at a gun shop, the prices come tumbling down, on occasion!
Jerry
