i'm not formiliar with US sources and brands. In europe, FFP-3 fold flat masks are sold by the brand VENUS, model:V-430-SLV

The are equipped with a metal nose shape thing (whatever they call it), exhalation valve and adjustable elastic bands. Being stored flat, they are very hard to crush.

The european FFP-3 standard is similair (although not identical) to the american N-100
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