Overgrown Forest, Apple Woods, Midnight Forest, etc. are good places to find Kecleon.
You already know what you need to have a chance to get it. (It's still 1/200, but it's higher than R/B)
Let's see... do you have Jirachi? Jirachi resists most of Kecleon's attacks. (I think Shadow Claw is the only one it doesn't)
It's on Final Maze 23F.
Now for the items...
Just bring enough Evasion Orbs, reviver seeds, etc. I used a One-Room Orb to recruit Kecleon, and it worked fine.
Did you know: Lopunny is based off a playboy bunny.