If you have a decent microscope and want to work on some citizen science that's directly related to the research in this article: https://www.vanettenlab.org/paulinella-consortium
She actually made some specific recommendations on the microscopy sub-reddit but they're a bit pricier ($425+). (scroll to last comment by Jay211TF):
https://www.reddit.com/r/microscopy/comments/1dhagyr/entry_l...
The samples were transported to the lab and observed at 100 to 400X magnification using an inverted microscope (IX51, Olympus, Tokyo, Japan).
A source for inexpensive high-quality equipment of questionable working order is whatever auction site your local hospital system uses to dispose of excess equipment.