Route 230, you got it.
You need to use the Pokeradar though. It won't show up normally. Use repels to keep wild pokemon away, and just use the poke radar. You cannot be on your bike either, and stand in the middle of the grass for best results, not on the edge.
22% chance, so you'll find some. If you find one, keep doing it. Look for the farther patches of grass after you catch the first and hope to "chain" them until you get one of the right nature