What equipment do I need to take photomicrography pictures?

If it is just as a hobby, you could try some workarounds. Try to play with a home made setup, 9x does not seem extreme:

if you want to use one, educational microscopes, the ones that meant for children or schools, can be kind of inexpensive.

You will need to attach to it the camera somehow, maybe with the adition of some spacer rings to be able to focus at shorter distances.

Polarized light is only an option, but if you want it, you can try with a polarized source, like the screen of your phone (probably not very powerful), or filtering any light with some polarized glass. You can use a photography filter or even sunglasses or any other polarized thing (like the inside of the old floppy disk, but will probably be too dark).

I have tried comparable setups in different applications, and even if the results are not comparable to using the real things, they were good enough to get relevant scientific data

There is an accessory called a bellows that goes between the camera body and lens and enables higher magnifications than macro lenses/extension tubes/diopter-add ons. Specific magnifications figures are determined by the focal length of the lens and the extension length used on the bellows.