The only way is the event pokewalker route, yellow forest.
The Light Ball is sometimes held by wild Pikachu. You can find Pikachu in Viridian Forest.
when tou battle red on his pikachu has a light ball you have to use theft to get it.
the only way is to get it from an event pokewalker route. when you are in the event, go to the yellow forest and you will find the light ball there.
You can't get a GS ball in Soul Silver. You can only get it in a Japanese Pokemon Crystal. Sorry.
You give it to a pikachu to power up it's moves.
in your mum
pokemart
No.
there is none
The GS Ball does NOT exist in the games.
faST ball
If you use the Pokewalker on the Yellow Forest route you may get it by taking 7000+ steps