Where can you capture a teddiursa in Pokemon Black?

You can't capture Teddiursa in Pokemon Black. Teddiursa is exclusive to Pokemon White.

If you want to add Teddiursa to your Pokemon Black team, you'll need to:

* Trade: Trade with someone who has Pokemon White and has caught a Teddiursa.

* Use a Gameshark/Action Replay: Use a cheat device to add Teddiursa to your game. However, this is considered cheating and may not be allowed in online battles.