any hardware store
Face masks are most effective at reducing the spread of SARS-CoV-2 when the infected persons wear them. They may reduce incidence of infection when donned by healthy persons, but they are much less effective at doing so versus the former case.
The N95 respirators one would likely find at a hardware store are not the proper masks. The 3M Cool Flow Valve Particulate Respirator 8511, for example, which I picked up recently at a hardware store, only filters the incoming air but not the outgoing air. The contagions flow straight out.
They were absolutely great for better tolerating the highly dusty environment that prompted me to purchase them. But I wouldn't trust them if contagions were the concern at hand.
If they are your only choice? Sure. But if you have a better option? Go for it. Help protect your neighbors.