The Official Pokémon Website has announced a distribution code for players of Pokémon Sun or Pokémon Moon to receive Sceptilite, Blazikenite, Swampertite, Cameruptite and Banettite Mega Stones.

Add a Handful of Mega Stones to Your Game

Use the following special code to unlock five powerful Mega Stones that can trigger Mega Evolution in battle.

Five more Mega Stones can now be yours when you enter the code below in your Pokémon Sun or Pokémon Moon game. With this code, you'll get a Sceptilite, Blazikenite, Swampertite, Cameruptite, and a Banettite, the Mega Stones necessary to Mega Evolve five Pokémon originally from the Hoenn region: Sceptile, Blaziken, Swampert, Camerupt, and Banette.

Mega Stones special code: MATSUBUSA

These Pokémon aren't available in the wild in Pokémon Sun or Pokémon Moon, but you can bring them into Pokémon Bank via Poké Transporter from earlier games. The Pokémon you transfer will lose theiritems in the process, however, so this distribution is currently the only way to get these Mega Stones in Pokémon Sun and Pokémon Moon.

To get the five Mega Stones:

1. Select Mystery Gift on the main menu.
2. Select Receive Gift.
3. Select Get with Code/Password, then Yes, and then Yes again to connect to the Internet.
4. Enter your special code.
5. Watch as you receive the Mega Stones.
6. Speak to the delivery person in any Pokémon Center to pick up your Mega Stones.
7. Be sure to save your game.

Go all-out the next time you battle with Mega Evolutions of these powerful Pokémon in Pokémon Sunand Pokémon Moon!

Source: http://www.pokemon.com/us/pokemon-news/add-a-handful-of-mega-stones-to-your-game/