Where do you get a master ball in Pokemon Silver?

after you defeat the 8th gym leader go to the dragons den once you get in to the den the 8th gym leader Claire will come bursting in and she will give you the TM flamethrower and the 8th gym badge go out of dragons den and professor oak or professor elm will call you and tell you to his office and he will give you a master ball.

hope this helped Daniel robertson