Here are some nice suggestions
You can catch Altaria in the dark grass on Route 14, but your plan might backfire due to Altaria's dragon weakness.
You can also catch Drifblim on Route 14, which has nice offenses and a decent speed, but it's defenses are terrible
There's Gligar/Gliscor on Route 11, which is pretty decent ingame with its nice defenses
Golbat can be found in the Strange House by Reversal Mountain, plus it's really useful when it evolves into Crobat, with its amazing speed and dual fighting type resistances
Hope I helped!