This is a very simple mouse with no/hardcoded software (only registers for basic configuration): https://www.nager-it.de/en/maus

It has an “as fair as possible” supply chain and can also be self-assembled. Detailed documentation is here: https://www.nager-it.de/en/informationen/material

Specifically for eduroam, I assume you can be tracked anyways, since you have to authenticate with your personal credentials, right?