If you gained access to the battle frontier you can obain these types of pokemon If you head to the battle palace you might be able to see an odd looking tree Head near the tree and use the Wailmer pail The pokemon will be a Suwdouodo at Level 50 Make sure you bring lots of Ultraballs and Timer balls

After completing the step above use a pokemon that learned surf and don't worry no wild pokemon will be there so don't use a repel After traveling the path you will see a cave The cave will be full of Smergles They're high level so I might suggest that you bring some level 60's and up