I know it doesn't solve all your issues but I've heard that some teachers are using a small speaker/microphone combo that hangs around your neck. Something like this is what teachers are using to breach the volume issues.
First of all, you should be able to wear (at least) an N95 mask during a global pandemic. I don't see how they could force you not to wear a mask legally if you care about your health. Secondly, I'd also look into a portable <strong>microphone and speaker</strong>.
We bought this model, which has a wired headset, to eliminate the possibility of interference among multiple teachers using these at the same time. I've had to replace a couple over the course of the year, but since they were only about $30, it was still a pretty good deal.