You won't get much lighter than the KLX hub as they are basically the 125/175 hub which were too light for the massive torque from the KLX.
No really, they used to break spokes all the time as the spokes were too light, maybe why there aren't many original spokes around now.
You would be better off getting some heavier spokes made than chasing originals, there are a few local spoke makers that could do this for you.
But back to the original question, I wouldn't mind knowing what the lightest cush drive hub is as I wouldn't mind going down this path as well.