Full Love 365 via eBay continues to offer this 6-Foot 6-LED USB Borescope Inspection Camera for $4.05 with free shipping. That's tied with our mention from a week ago as the lowest total price we've seen. (It's the best deal today by $2, outside of other eBay vendors.) It features a waterproof camera and 640x480 maximum resolution.
Expect this item to arrive in two to four weeks.