I don't, there are tons of reasonable options on the new market and even more on the used. If you can find something by Nikon, Zeiss, Olympus, or Leica (the big four of microscopes) on the used market with a 40-100x objective, complete, and looking like it was made in the last 40 years, it would be hard to beat especially under $100 almost regardless of model.
If you're looking for new microscopes, Amscope is an easy default that offers pretty decent features and image quality without a lot of expense, but in terms of model, you want a compound microscope with brightfield/transmitted illumination, 10x or similar eyepiece(s), and a 40-100x objective (and some lower, definitely). While not a guarantee of quality, I think for a non-digital microscope, a binocular design is better than a monocular on average (they're more expensive to make, so they are often overall better, and there are basically no monocular scopes in the more premium categories), with trinocular (a camera port as well) is still more desirable.
Most digital microscopes will be reflected illumination (not transmitted) and will be of more limited use for single cell organism ID. They often have longer working distances (correlates to lower sharpness for the same magnification, but not always the case), and may not come with a particularly good stand/focus mechanism. The fully variable zoom is super handy, but trades off performance at high magnification for this, that's why a lot of microscopes still use individual objective lenses.
If you're working with higher power objectives, remember that having a coverslip and sometimes immersion oil (the objective will be marked "oil") is often imperative to get best optical performance, so getting a little accessory package with slides and coverslips is very useful. Especially so with single cell ID, since the depth of focus at high magnification is so shallow, you really want the sample to be very, very thin, so a flat slide, a drop of your subject, a coverslip on top, and then wicking out extra water through the sides of the coverslip with a piece of paper towel or something will help get a clear image.
And the age old marketing counterpoint: higher magnification is not necessarily better. You should be aiming for 400-1000x total system magnification (objective times eyepiece in the standard microscope category), and the image you see will not be getting any sharper than you can see at 600-700x (or maybe 800-900x with oil immersion), though it does get bigger. That means your 100x objective will make the target you're looking at bigger, but probably won't make it much sharper than the next lower power objective, and you'll need brighter illumination to see through it. This can still be useful by eye, but less so with a camera, and using 15x -25x eyepieces gets you the size increase (and light decrease) without any improvement in actual image sharpness. Seeing microscopes that advertise 1500x+ magnification is entirely a marketing gimmick and doesn't represent optical performance.
