I imagine that just like my grandparents who lived through the Depression hoarded ketchup packets despite being financially secure, as soon as N95 masks are freely available I will keep a stash handy for the rest of my life, regardless of whether I ever face another pandemic, or official organizations advise against it.

We could improvise them though. I know in Hong Kong they have asked people to improvise using layered paper towels and tissues because those are readily available nonwoven fabrics.

It isn't as good as the real thing, but done at the population level I expect it would lower the reproductive value of the virus and thus help flatten the curve.

You can make your own cloth mask.