A regular dust mask from Lowe's or Home Depot would do the trick, but if you want to spring for a 3M half face respirator you can usually find one that has a combination particulate and vapor filter cartridge. P95 or P100 filters are your friend for anything cementitious you are grinding. Very occasional grinding with a dust mask will not be too bad, but repeated exposure damages your lungs. Just make sure to ventilate the space well and maybe try to use a shop vac to capture the dust as you generate it or even consider using water as you grind to cut down on dust even getting into the atmosphere. A respirator is an easy safeguard though in case you don't want to mess around with all of the other dust control systems. Make sure it's snug on your face though

Technically, any mask meant for filtering breathing air is a respirator. N95 is alright, we called for that any time concrete would be cut or drilled dry. But you would need to take care that it's fitted well. If you can't find any regular masks that fit well you might need to go with an elastomeric half-mask or something.