Only ones that I found that could go that fast is the
Phoenix racer 7240 kit with 72v battery
BMC 600 watt with at least 66 v battery
or maybe the PHoenix Cruiser with a 72v battery
Hi-powercycles.com and cycle9.com have the BMC.
You can find the phoenix racer at amazon.com and electricrider.com and probably a few other places
With the BMC, it'll get you to 40 mph with lighter batteries since it's a lighter motor. That'll cost you around $1600. I've already looked it up since I have the same interests.
The Phoenix Racer kit is $1200 if you don't mind 40lbs of batteries that are SLA . If you want better batteries, it'll cost you close to $1800 - $2000