A few weeks ago I found a cheap used inverse microscope, supposedly for kids, “Telmu inverse microscope”. The mechanics were crap but it did have a sturdy revolver with din objectives. After initially trying to mount a Raspberry Pi v1.2 camera module into the tube, I eventually scrapped the whole thing for parts.
I designed a quick and dirty C mount adapter to mount those DIN objectives on the Raspberry Pi HQ camera with FreeCAD. I have several Heights available, and you can make your own by changing the parameters in the spreadsheet. The longer versions are most necessary/useful for the lowest magnification lens. I know virtually nothing about optics, long ago it was a topic in some kind of physics for Veterinarians class. The model is parametric though.
The picture quality is quite ok.