in the vilstone warehouse next to the galactic building
You go to Vielstone city and go into Team galactic building and find Cyrus(Team galactic boss) then battle him. After the battle he should give you a master ball.
You can find it either sitting on a route like you find most TM's, you can buy it in Vielstone City Department Store for a hefty amount of cash, or you can trade in coins at the Casino's prize trade in building in Vielstone City next to the Casino or you can find TM35 at the Fuego Ironworks.
talk to the team galactic guy in front of the team galactic building.(In veilstone city)
vielstone city
you can find it in Eterna city on the top level of Team Galactic Building
one of the scientists near the end of the game, i think in the galactic hideout in veilstone
look outside the bigger building on the right hand side of vielstone up the stairs
u can find him in the galactic building in veilstone (p.s its not the galactic ware house
hes in the team galactic building and u have to rescue hin
Some Galactic will drop it. How silly.
simple, just get into the warehouse, find Cyrus in the building, destroy him, find Saturn, defat her, and poof, they leave.
You find him at the Vielstone Building, aftergoing to Lake Acuity, after getting seven badges.