(Hope this will help)
In Pastoria City, there is a guy who reminds moves of Pokémon. If you go there with your Scizor, he can teach your Scizor Bullet Punch. (Heart Scale needed if you want to do this)
If you don't have a Heart Scale...then do the following:
1) Go underground.
2) Fish for wild Luvdisc (next to Pokemon League). Covet/Thief it or catch it, then snag the item. If it doesn't possess one, repeat the process until you find the scale attached to it.