How do you get pic related?

>>30080972
Uh, buy them from the shop or try to get one at a pokestop duh

>>30080972
kukui gives you one after you beat the elite4

>>30081057
Oh, so it's post-game? Oh no.

>>30081057
Hmm? Wasn't it for catching 50 Pokemon in the Pokedex?

>>30080972
You need to talk to kukui after you've filled 20% of the alolan pokedex. That doesn't mean postgame, it doesn't mean anything aside from that. You can get it before the game ends.