Here. This will it's locations in every game that it is possible to find a Starf Berry in.
>- Emerald: Given away by Scott after the player has obtained all seven Gold Frontier Symbols.
- HeartGold and SoulSilver: Obtained after taking 9,999,999 steps on the Pokéwalker.
- Pokémon Battle Revolution: Can be purchased in Pokémon Battle Revolution for 38,400 Poké Coupons.
- Black and White: From a Trainer on the Battle Subway platform after 203 consecutive victories.
So yeah, it's pretty rare and it'll take a load of effort to get.
It is possible to grow Starf Berries in Gens 3 and 4, if that counts as a location.