According to Canon sources, there are several settlements that fit the "Mos -" naming convention other than the two which appear in the films:
Mos Doba, which appears in the 2014 mobile game Star Wars Commander. Its location is not specifically given.
Mos Elrey, which appears in the Star Wars: Complete Locations reference book. It is located in the Western Dune Sea, at the edge the Jundland Wastes.
Mos Entha, which likewise appears in Star Wars: Complete Locations. It is located "across from" the Mospic High Range, a mountain range between Mos Espa and the Dune Sea.
Mos Pelgo, which appears most prominently in The Mandalorian, which is only specified as being in the northern hemisphere of the planet.
Mos Taike, another place appearing almost exclusively in Star Wars: Complete Locations. It is located on the edge of the Northern Dune Sea.
and last and certainly least,
- Mos Zabu, a place mentioned only in episode 3 of Star Wars: Jedi Temple Challenge, a children's game show on StarWarsKids.com.
There are, of course, settlements on Tatooine that do not fit the "Mos- " naming convention, but that is outside the scope of your question.