There are a few methods:
- Zabolous Forest in Gilgoles: Use Alice’s Pilfer on the tree enemies.
- Equip Emerald with the Bandido Knife and use Treasure Eye on Trent enemies (Cockatrice Forest).
- Balto can bring it back if he’s above level 35.
- You have a chance to retrieve it from the big bridge above Acquia on a rainy day (sparkly point in the water).