Through my experience of talking with researcher, modelers, govt officials, mask maker, purifier companies, and activist groups in this field is that: one should just start with A MASK. It doesn’t have to be perfect. Think if you’re just procrastinating on acting on a health emergency?
Average specification I believe: N95 mask with one valve is great. My first suggestion for where to buy is always SmartAir. Here’s the shop link. They have variations and for kids too.
Note that the mask market has not matured like other consumer markets, you probably won’t find that perfect mask for you, there are multiple factors that decide if the mask will be effective, comfortable, affordable, accessible to you.
Some are: effectiveness (% PM blocked), fit (how air-tight it is vs comfort), breathability (breathing out is natural), humidity control (a good valve helps avoid accumulation inside), number of valves (balance between comfort and effectiveness due to reduced surface area of filter), filter mechanism (embedded in the mask vs removable), mask usage (can be washed vs disposable), fit-test (some like Totobobo let you test the fit DIY), cost (one time for a cloth mask vs recurring filter costs), aesthetics (how people react to it, how it makes you feel), nose-metal-strap (ensures fit on the top, nose shape affects, people with glasses), accessibility (available on Amazon or have to import, local store?, filter available?), customer service (does the seller help with usage/ technical questions?).
Surprising to many, empirical tests have shown even a surgical mask (which we see in hospitals everywhere) are significantly effective [Reference]. The point is not that one should get surgical masks and be done, but realize that the most important thing to do is to accept the problem and start with SOME solution (i.e. any average mask). Start and then observe how the mask is working for you. From the points I mentioned above, which are good for you, what bothers you, do you find the single valve sufficient, does it feel so tight that you probably will stop using it in summer…so get a new one. This time you know exactly what you want. And at the end again going back to the earlier point, you probably won’t find the perfect mask, but definitely a better one.