Over the years I've been able to assemble a basic set of medical supplies, some from outright buying equipment like my manual BP cuff and stethoscope. But if you like to go to rummages and yard sales you can find some interesting stuff there. I picked up an old microscope, all it needed was some cleaning to be fully functional. Actually ran across a really nice binocular model later on for $15 but it didn't have a mirror as an option for a light source.

Found a dissection kit, picked it up because of the scalpel. Reusable and can be sharpened.

I have nursing manuals from the 1930s that talk about how to process equipment and supplies for sterile use from a time before modern custom packs with disposable everything. Old lab manuals that teach you how to make supplies rather than order them and do tests with fundamental equipment instead of loading a sample into an automatic machine that requires proprietary cartridges. Old pharmacy manuals that tell you how to prepare medicines and assay them for effectiveness. This is a niche that a prepper's library can fill.

It's not that I'm a medical professional but I hope to work with them in a collapse to provide the safest care that we can provide under the circumstances.