I picked it up off Amazon. It was $40 bucks. Not the greatest, but if you hold your breath just right it works ok. Took quite a bit of fumbling around to capture the pic of the edge...very hard to focus. I had to remove the plastic shroud so I could get the blade close enough to focus. The button that allows you to take pics is near impossible to use at that magnification. Throws the microscope out of focus when you try to snap the pic. I resorted to doing a print screen from the PC.
Here is a link to the one I picked up. Really not all that impressed but will make do.
AGPtekŪ USB 800X Digital Microscope endoscope 2MP 8 LED Compatible with Windows and Mac OS 10.5 or above For Micro-measure Work:Amazon:Industrial & Scientific