Underground. Use Explorer Kit, then dig around.
The Underground
there is none sorry
There are two ways to evelove Pokemon in Pokemon platinum by lefstones and leveling up.
You can find stones undergrounds.
A few stones can be found elsewhere but majority is underground ( NO TRADE STONES )
Iron Island.
Togetic into Togekiss and Roselia into Roserade
You can find stones Underground. You take the explorer kit and then go underground.
the same way as platinum
there is one in mt.cornet and the other one is on battle island on a a ledge in the survival zone
Catch, train, evolve, trade, breed, use stones, restore fossils, raise friendship, and have them learn specific moves. Those are all the ways all the Pokemon are obtained.
there is this guy in the sea at sunyshore city then you talk to him and he changes all the shards into stones or you can buy the NDS action replay ultimate code for Pokemon and get 999x stones of every kind