Niantic has added
Gym Leader Avatar Items to Pokémon GO. There are three varieties of the tops, shorts and shoes, one for each team but they also require a certain Gym Leader medal rank to be able to purchase.
Gym Leader Avatar Items
Trainers, are you an expert at defending Gyms? Show off your team pride with new Gym Leader avatar items! Depending on your Gym Leader medal rank, pieces of this outfit will be unlocked and available for purchase.
Gym Leader Top: 220 (requires gold Gym Leader medal)
Gym Leader Shorts: 200 (requires silver Gym Leader medal)
Gym Leader Shoes: 100 (requires silver Gym Leader medal)
Gym Leader Gloves: 50 (requires bronze Gym Leader medal)
Source:
https://twitter.com/PokemonGoApp/status/978427895696822272