I have been wearing a P100, 3M 6000-series half-face respirator everywhere I go in public for the last 5 years (genuinely far more comfortable than any other mask I’ve ever worn). I have particularly compelling reasons why I feel this is necessary. In my experience, it’s an effective measure, and I literally teach high school 8 hours a day with it on. In my experience, the trick is this:

• What the other people around you think of you is absolutely meaningless. Doesn’t matter. Ignore them.
• if someone wants you somewhere badly enough to demand you go out of your comfort zone, then they want you there badly enough to be brought out of their own comfort zone by having Darth Fucking Vader show up.
• People who look at you weird are not people you want to be around. People who ask you why you are wearing it are worth a brief explanation, and the simple fact is, nobody really gives enough of a shit for it to matter.
• I have gotten very good at not inhaling when I don’t have my respirator up, so I’ll take it off momentarily to explain the situation to anyone who asks, and they are, 19 times out of 20, immediately understanding and we both go on with our days.
• You have to make your own threat model. For me, I’m to the point where I’ll downgrade to an N-95 in my therapist’s office (since we’re 1-on-1 and nobody else has been in that room for 15 minutes) and when I go to a triannual game night at a friend’s house, because i know they’re all vaccinated, and I trust them to tell me if they’re sick.
• Outside of some place like Japan, where societal pressure has led to an actual culture of hygiene, propriety, and basic consideration of others, you simply cannot assume that people give a flying fuck about their effects on the people around them. In a million ways, from cutting in line or on the highway, to playing music or a phone call on speaker on public transit, to the myriad externalities of the way they live, they inconvenience you and others around them. This is, unfortunately, normalised throughout most of the world, and bad hygiene surrounding infectious disease is just another part of that. Unlike playing music on a bus, however, poor infectious disease hygiene can lead to someone else’s death. You have to decide the precise level of risk and investment you’re willing to accept, and fuck anyone who disagrees with you. They can either deal with your non-negotiables or not. Set a clear fucking boundary. Rather than demanding that they act in accordance with your whims, judge by their past actions how they fit into your threat model and inform them of your new criteria by which you feel safe to engage with them and the world.