Where to buy timer balls in Pokemon black 2?

You can't buy Timer Balls in Pokemon Black 2. They are a rare item that you can only obtain in specific ways:

* Battle Subway: You can sometimes find them as rewards for winning battles in the Battle Subway.

* Rotating Items: They are sometimes available in the rotating item selection at the Pokemon Center in Castelia City.

* Rare Item Encounters: They are rarely found as an item dropped by wild Pokemon.

Remember, Timer Balls are extremely useful for catching Pokemon that are about to faint or have low HP, so if you find one, hang onto it!