Where can you buy the Rain Dance TM in Pokemon Platinum?

You cannot buy the Rain Dance TM in Pokemon Platinum. You can only obtain it through the following methods:

* Find it in the wild: Rain Dance TMs can be found in the wild, hidden in the grass. This is the most common way to get it.

* Receive it as a reward: There are certain tasks or events in the game that will reward you with a Rain Dance TM.

* Trade for it: You can trade with other players to get a Rain Dance TM.

However, there is no specific location or shop where you can directly purchase it.