how to get two eevee eevees pokemon platinum

[Galaxy]

how do i get 2 evee eevees in pokemon platinum?

[Zidarose]

There are very few ways to get more Eevees in the game:
If early on, hope to get a Female from Bebe (or keep resetting the game until you do) then breed that one once you can at the Daycare

If you got a male and stuck with it, then you want to snag a Ditto so you can breed that with your Eevee to get more Eggs

Another Option is after you clear the game and have the National Pokedex (by seeing all 210 Pokemon in Platinum), you can head to the Pokemon Mansion's Trophy Garden and follow these steps to get an Eevee:
1) Beat the game and see all 210 species of Pokemon in Platinum
2) SAVE before talking to Mr. Backlot
3) Talk to Mr. Backlot, if he doesn't say "Eevee", reset

Without the save prior, you will only encounter whatever Pokemon he happens to mention before hand for the rest of the day.