Health supplies are not exactly widely available right now. It isn't unreasonable to suggest that you put the needs of front-line workers ahead of your own. As long as you keep track of your own hygiene (which you do), and as long as you're sticking to government advice (which you are), then why seek an expensive product that you don't need but that someone else will?
If, in spite of all that, you still want to buy a mask, then you should probably check out N95 masks. Remember that you'll need several, as, for obvious reasons, you shouldn't use the same one for too long.