Once you beat the Elite Four,You can get one from Bebe.

u haf 2 get the national dex ,then talk to Bebe the hot computer geek. breed it with ditto 6 times so u have 7 in all so u can get all the forms of EeVeE and u cant get a ditto in the game u haf 2 get emearld go to Fallarbor Town then 2 the fossil maniacs house and go 2 the cave Desert Underpass and if u go in the middle of the cave u can catch it. then migrte the ditto in2 the pal park catch it, and u have a ditto. (this is what i used, and it DOES WORK, U JUST HAVE 2 DO A LITTLE WORK.