e-vipcom Store via eBay offers this 49-Foot 6-LED USB Endoscope Inspection Camera for $17.35 with free shipping. (Select 15 meters.) Aside from other eBay sellers, that's the lowest total price we could find by $19. It features a waterproof camera and 640x480 maximum resolution.
Note: expect this item to take four to eight weeks to arrive.