Where to get Eevee egg in Pokemon diamond?

The following Pokémon can only be obtained or encountered after seeing the 150 Pokémon in the Sinnoh Dex and then speaking to Professor Rowan in Sandgem Town. Don't worry, you don't have to catch all 150 - just see them. Plus, it's pretty easy to do that as long as you fight a lot of Trainers.

Eevee

In the house right next to the Pokémon Center in Hearthome City, Bebe, the computer geek who maintains the Pokémon Storage System in Sinnoh (think like Bill or Lanette from previous games), will give you a free level 5 Eevee if you talk to her and have room in your party.

Eevee is very good for breeding with lucario.