There is no legit way for non-Japanese players to get Celebi. In Japan people who pre-ordered Colosseum got a bonus disc that allowed capture of Celebi after completing the game, but Americans got Jirachi instead and I'm pretty sure we got none.
What Pokemon did you start with? Depending which one, one of the Dogs will be running around the map. If:
You chose Bulbasaur - You get Entei
You chose Squirtle - You get Raikou
You chose Charmander - You get Suicune
Also, by fixing the machine with the Ruby and Sapphire, you can now trade with Ruby, Sapphire, Emerald, Colosseum and XD, giving you the capability to expand that National Dex.
31/05/2007
Pokemon Diamond
Sydney, NSW