Camera suggesion for rostrum with SDK (and wifi)

I currently take photos of paperwork using an SLR mounted to a rostrum stand. I have written my own software which uses the Canon SDK to take photos of the paperwork, recognizing QR codes on the paperwork.

The camera I use is a Canon 5D Mark ii with an L lens. It’s total overkill for the job! I’d like to have a camera permanently setup for this purpose, and feel that there might be a domestic point-and-click camera which I could pick up second-hand that would do the job.

Does anyone know a camera that meets the following specs?

• Take photos of A4 paper at a distance of 30-50cm. (I currently use my 17-40 L lens on the 35mm camera)
• Can fit to a rostrum with a standard tripod thread.
• Is powered over USB cable.
• Has an SDK available that means that I can communicate with the camera over USB or WIFI to take and receive photos remotely?
• Is inexpensive and available on the secondhand market.