You don't want ZERO float, you want something without free float, that rapidly ramps up the spring rate. You might like road pedals more because of the flat back as well as Speedplay road pedals that you can lock down. I didn't like the feel of crank bros in any case.
Usually the float is controlled by the cleat. I don't think ANY MTB cleat is wide enough to feel like you have zero float. I'd borrow a set of someone's shimano road cleat /pedal with the flat back side and start there. Maybe you can try it at the LBS.