How do you get the badge that will let you surf whenever you want Pokemon gold version?

Defeat Morty the Ghost-type Gym Leader. he will give you the Fog badge which will let you surf and make all Pokemon up to level 50 to obey you.

Defeat Morty the Ghost-type Gym Leader. he will give you the Fog badge which will let you surf and make all Pokemon up to level 50 to obey you.