There is only one Master ball in Pokemon diamond so use it wisely. I hope you can find it!
Find an action replay code and program it, that's how you get many masterballs on Pokemon diamond action REPLAY. ;)
You can get 2 Master Balls in both versions.
you can get 1 master ball
1
i masterball
1
one
he will randomly give you any pokeball, excluding premier balls (buy 10 pokeballs to get one), cherishballs (balls containing Pokemon obtained at a special Nintendo event, a legendary mostly) and master balls (100% chance of catching ANY Pokemon. (only ONE in each game.))
You can clone a Pokemon with the master ball or trade it to a friend and keep starting over until you're satisfied with the number of master balls.
Attach your master ball to ONE POKEMON, next CLONE that Pokemon for how many master balls you want. Next detach them, and release all the clones (if you want)
Duplicate Pokemon with a masterball attached to them.
in all of the Pokemon game, the way to get a master ball is to beat the boss of the criminal organization and you will get this as a reward. but i heard that you can get more master balls in pearl, diamond and platinum in jubilife city in the tv station by that lottery stand but i think it will take a lot of trading with many trainers to get one master ball just to match the numbers. but i think there is a cheat to get A LOT of master balls. I hope that this answer is helpful to many owners of these Pokemon games.