If you can be bothered to breed another Lucario, and level it up to 100, I have an ideal Lucario moveset with egg moves from Smeargle and Blaziken:
Lucario @ Lucarionite
Ability: Inner Focus
Evs: 252 Atk / 252 Spe / 4 HP
Nature: Adamant
Meteor Mash (bred from Smeargle)
High Jump Kick (bred from Blaziken)
Extreme Speed (Level Up)
Earthquake (TM Move)
If you can't be bothered to rebreed, then you can put Earthquake on as it covers lots of types. Close Combat is probably the best fighting move your current Lucario can learn, due to its high power. So, either:
Rebreed Lucario
Meteor Mash
High Jump Kick
Extreme Speed
Earthquake
Current Lucario
Close Combat
Extreme Speed
Bullet Punch
Earthquake