@mcc @clarity @karen SO recommends Airinum, "Urban air mask", which is apparently KN95 rated/N99. It's currently 40Eur on their site plus shipping, which is a bit much even with included extra filters, but SO says they saw it for much cheaper on ie ebay uk so there might be an alternative for you too, potentially.
Also they have never caight covid, even after travelling internationally a few times, so it seems to work 😅