Yes it's absurd to pair a nice microscope with a cheap low resolution usb camera but it's what I had on hand and it ends up working surprisingly well.  The design should be easy to adapt for whatever similar usb microscope you can source.  I printed it with eSun ePA-CF (carbon fibre filled nylon) at 200 micron layer height, which works beautifully if it's very dry.  The adaptor mounts to the eyepiece with a snug but not too tight fit, and has a captive m3 half nut and bolt as a set screw to tighten the inner ring onto the microscope eyepiece.  The usb microscope just sits in the adaptor, gravity is enough to keep it in place.  This USB microscope has a clear plastic part at the bottom which should be removed for the focal length to work out correctly for this setup.

Print without supports - there is a built in support ring for the inner lip which easily pops off.