Question

Is it possible to get more than one Master Ball in Sun and Moon?

Comments

Sad but true fact: you have a better chance of finding a masterball on the GTS than you do winning the lotto.  You'd be surprised how many people are so desperate that they give their Pokémon a Masterball to hold in the hopes that people will jump at the chance to trade for it. If you can find those and trade for it, it's as simple as that

Answer 1

Yes.

Go to Hau'Oli city, then go to the alola tourist bureau, its somewhere on the right of Pokemon center, between that and your house, Or 1 building next of the right of the mall I should say. Play the Loto there by talking to the girl on the left. She will give you a number randomly, if it matches a number any of your Pokemon trainer ID, It will reward you if a number matches of Trainer ID:
1 Number Matches: Moomoo Milk
2 Number Matches: PP Up
3 Number Matches: PP Max
4 Number Matches: Rare Candy
5 Number Matches: Masterball
You can only do this once per day though

Answer 2

Yeah, from the Lotto-ID Center in Hau'oli City. But its impossible so don't get your hopes up :(

Source 1
Source 2