Pikachu can be found in the Viridian Forest and there's a 5% chance of a Pikachu holding one. A good plan of action in regards to hunting for items is to have a Pokémon at a very high level leading your party that has the Compoundeyes ability because this will increase the chance of running into wild Pokémon that will be holding items. Additionally you should have a Pokémon with you that has the Frisk ability as well as either the Thieft or Covet moves.A
Also the special Event-only Pokéwalker course Yellow Forest has this item after 7,000 or steps.
when tou battle red on his pikachu has a light ball you have to use theft to get it.
You give it to a pikachu to power up it's moves.
You can't get a GS ball in Soul Silver. You can only get it in a Japanese Pokemon Crystal. Sorry.
no
snorlax
silver apricorn
the silver apricorn
If you use the Pokewalker on the Yellow Forest route you may get it by taking 7000+ steps
latious
The Goldenrod Underground.
prof. oak
you can only get a cherish ball from Nintendo event