Pokemon Diamond; seeing 2nd generation starters

I'm playing pokemon diamond, and I'm wondering if there is any other way(from getting them from emerald) of getting 2nd generation starter data? Such as seeing them with any trainers? Anybody know if there is any trainers that carry any of them?

If you put a GBA Pokemon game in the bottom slot of your DS, you can find first, second and third generation pokemon

in your diamond IF YOU BEAT THE ELITE FOUR. It may take a while to find them, though.

If you put a GBA Pokemon game in the bottom slot of your DS, you can find first, second and third generation pokemon

in your diamond IF YOU BEAT THE ELITE FOUR. It may take a while to find them, though.

Arceusmaster

You need the National Dex to trade them to your DS game.

The only other method that I can think of doing this (besides Emerald), is with Pokemon Colluseum for the GameCube.

You need to beat Cipher's Boss, Evice to unlock trading with GBA Pokemon game paks. You trade the Meganium, Typhlosion, or Feraligatr, that you snagged in Phenac City early on in the game. Once traded to your GBA game, breed it with a Ditto to get the Chikorita, Cyndaquil, or Totodile egg and hatch it.

Do this and you can Migrate the newly hatched Pokemon to your D/P Game card. Just be sure to breed and leave another of the same Pokemon behind in your game pak.