Once the lens assembly of the C920 is removed, this adapter can be used to mount the image sensor directly over a 25mm microscope trinocular. The 25mm ID mount fits over the camera adapter of the Amscope SM-3T/SM-4T series, which uses this head and adapter:
http://www.amscope.com/7x-45x-trinocular-zoom-stereo-microscope-head.html

Friction fit on microscope side, M2.5 mounting holes on camera side.