- The Elite Four members have Sitrus Berries that you can steal. Drapion has it with Aaron, Rhypherior has it with Bertha, Magmortar has it with Flint, Gallade with Lucian, Garchomp with Cynthia.
- Your rival has Sitrus Berries on his starter Pokemon starting from the Pokemon League battle.
- Cyrus has Sitrus Berries on his Murkrow and Honchkrow. His Weaviles has one in the last battle in the Distortion World.
- Mars has an Oran Berry on her Purugly in the first battle in Valley Windworks and a Sitrus Berry on every battle afterward on Purugly.
- Jupiter has Sitrus Berries on her Skuntank in every battle you have with her.
- Saturn has Sitrus Berries on his Toxicroak in every battle you have with him.
I'll edit if I manage to find more.