I have Pokemon Y and pretty much all my friends have Pokemon X and I was wondering if I can get the Y-exclusive mega stones more than once so I can trade for the X-clusive (#badpuns) ones.
I think you may be able to buy extra for charizard at the shop since it is a starter Pokemon, but I'm not sure if they sell out or not without going back. You have to do another play through for the rest since they are only found once in the game. You either have to trade them to your friends or the pokebank trial, and then back to your game. You can also get some extra starters and the event torchics this way.