1. Inside Aqua Hideout 2. Trade it from a friend. (If you play Pokemon Emerald, you can clone it then send one Master Ball back to your friend) 3. 1th price in the lottery in Lilycove City. (it's very very very hard to win) 4. Use cheats like Gameshark or Action Replay. (Not the safest way. Not recommended) 5. Or you can start a New Game.