I think the only pokemon that can get Volt Tackle is Pikachu,catch a Pikachu that hold a light ball,theres very little chance that a Pikachu can hold a light ball,most of the time,it hold a oran berry.This is how I did it,it was in Pokemon Pearl,but I think it goes the same.I went in the trophy garden at the grassy area,I use a honey,and it lure out a female Pikachu, I caught it ,and it was holding a light ball,then I breed the Pikachu thats holding a light ball with a male Pikachu in the daycare, and got a pichu egg,when it hatch, it knows Volt Tackle and it has a Pokerus.
Its easy go to the trophy garden catch Piacatu hold light ball day care
DONE!
DONE!
Go to a person in solecean and ask a girl in the poe mart not the cashiers the people the are looking for stuff
Catch a pikachu give a light ball to it then Picchu it then in near by grasses find the pikachu and catch it again it should have volt tackle now, apply to Picchu,pikachu, and raichu