In our Pokemon Sun and Moon PokeBalls Locations Guide, we have shared the locations of all types of PokeBalls that you can get in the game. You can find the Dive Ball in Route 8, Route 15 ...

A high-performance Poke Ball which has a higher success rate of catching Pokemon than the Poke Ball. You can buy these Poke Balls from the Poke Center but you can also get them from NPCs.