And Onix gets it at 14. You're probably working with the NPC Trade one so boosted EXP, but your only good grinding spot is the Spout Tower. Which is bad for Onix and Geodude both for obvious reasons.It also doesn't help his ace is level 9. For the record, Geodude learns Rock Throw at level 11. You have to deliberately overlevel in order to have a good tool against Noctowl, and that's ignoring Mud-Slap screwing with the accuracy.
The other potential option is Mareep with Thundershock at level 9, but I cannot remember if you're allowed into Route 32 before beating Falkner.