TL;DR: There is a place you can buy masks online without contributing to a local supply shortage.
The majority opinion on Less Wrong appears to be that masks are beneficial for reducing the spread of COVID-19 but that you should not buy them because doing so would contribute to shortages for health care workers and the immunocompromised. If this is true then it may be possible for you to do good for your community by importing masks from somewhere that has a surplus. According to my friends in China, they have the disease under control and there is a surplus of masks there.
You can buy consumer products from China on a website called AliExpress. Don't pay more than 13-16 Yuan ($1.86-$2.28) per mask (not including shipping). If you can't find a price cheaper than that, message me first instead so I can put you in touch with a friend of mine who has N95 masks in stock.
I am not affiliated with AliExpress. ↩︎