Masks
In general, N95 masks are now widely available. The most important aspect is that it has a good, personal fit and seal. Additionally, not having an exhalation valve is a kind feature to your neighbors. The full list of NIOSH (National Institute for Occupational Safety and Health) approved N95 masks can be found here.
If, for any reason, you are unable to find any N95 masks, KN95 masks are reasonable (caveat: the FDA had authorized a number of KN95 masks for emergency use, however this order has since been revoked; there are no guarantees on the current quality, but the prior list of masks with Emergency Use Authorization can be found here).
3M Aura (Model 9205+)
Great comfort and fit for longer periods of use while getting a great seal (adujstable nose band). However, the elastic band is prone to breaking.
Merilogy
Easy to use and folds nicely. However, the seal is not as good for smaller faces and there is no metal nose band.