The only way to get Light Balls is to take them from wild Pikachu as held items. Each wild Pikachu has a 5% chance of holding a Light Ball, and when you find one you can either catch it and take the item, or use an item stealing move.
Wild Pikachu are only found in the Trophy Garden behind Route 212’s Pokémon Mansion.
Getting Light Balls
Every Pikachu you encounter in the wild has a chance of carrying a Light Ball as its held item.
Usually, the odds that a wild Pikachu will be holding a Light Ball are 5%. However, you can vastly raise those odds by putting together a dedicated item-farming team, which uses the Abilities Compoundeyes and Frisk to make the process much faster.
Wild Pikachu are only found in the Trophy Garden – this is the tall grass behind northern Route 212’s Pokémon Mansion.
So when you’ve found a wild Pikachu holding the Light Ball, either catch it, or use a stealing move like Thief or Trick to obtain the item.
Once you have the Light Ball you can end the battle however you prefer; you’ll hold on to the item even if you flee.
What Does the Light Ball Do?
The Light Ball is a held item that doubles a Pikachu’s Attack and Special Attack stats.
This is a strange and interesting item, since it works only on a Pikachu (even Raichu can’t use it). And at first it seems like the Light Ball would turn a Pikachu into an electrostatic powerhouse, allowing the speedy Pokémon’s Attack and Special Attack stat both to reach 100+.
Unfortunately, Pikachu’s defenses are appalling—even worse than those of Kadabra and Haunter.
Moves like Substitute can help stall the inevitable KO. But if the Pikachu is hit by even a moderate attack, it’s unlikely to get back up.
A Light Ball Pikachu is a fun Pokémon to surprise casual opponents with, but if the goal is to win the match at all costs, go with another option.