Game questions goes in the game forums. Q&F is for site PC questions only.
But I'll help you,
Jirachi can be found in the bonus disk with you pre-order Pokemon Colosseum (I'm not sure where you could find it now since it has been like three months ago since Colosseum came out).
Chemcho can be found on top of Mt. Pyre. There is a spot of grass on the very top where you get the Red/Blue Orb.
Deoxy I think can be found in Fire Red and Leaf Green.
And I'll move this to R/S.
*Moved*