Highest lighting damage (or cold damage) I can stack?

I want to try a melee bd that utilize the easy lightning vulnerability, add as much lightning/cold damage to my weapon attacks. The ones I can think are sparks from equipment +1, Draconic Elemental Weapon + 1D4, up-cast elemental weapon +2D4, charge-bound warhammer +1D6, giant subclass elemental cleaver +1D6. That's only about 6~25 damage, double for 12-50. Still quite low, any thing I'm missing here?