You can't but when you Defeat Cyrus in the Galactic Veilstone building and he will give you it.
To get more than one Master Ball, you must trade Pokemon that are holding them to your game.
You get it with an action replay
it requires an Action Replay. if you can activate without one, then i don't know how to
Find an action replay code and program it, that's how you get many masterballs on Pokemon diamond action REPLAY. ;)
yes there is
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action replay is best
i suggest action replay or win the lottery
get an action replay
ACTION REPLAY
yes. its master ball cheat
You cannot find a second master ball however you can trade Pokemon to get another Pokemon with a master ball or use an action replay