Niantic has announced that players of Pokémon GO will be able to get tropical Alola region inspired outfits in the game to celebrate the launch of Pokémon Ultra Sun and Ultra Moon.

New Avatar Items Inspired by the Alola Region Available in Pokémon GO

Trainers, We’re excited to announce that new avatar items are now available. To celebrate the upcoming launch of the Pokémon™ Ultra Sun and Pokémon™ Ultra Moon games for the Nintendo 3DS™ family of systems, you’ll be able to dress your Pokémon GO avatar in brand-new outfits inspired by the tropical Alola region and worn by the main male and female characters in the games, which launch on November 17.

Source: http://pokemongo.nianticlabs.com/en/post/ultrasunmoon