Not that I'm aware of. Probably have to get one of the manual lenses...the 16x or 14x which is a rare one to find. I believe the 14x has the "real" apeture ring on the lens while the 16x is done thru the camera body and is not stepless. Another thing to consider is the front element of both lenses. If I remember correctly, the 16x lens doesn't rotate, but the 14x one does. So if you're thinking of putting a matte box, filter etc... on the 14x lens, it will rotate should you wish to change focus.
But to get that jet zoom you want (me too!!), these lenses are the only ways to do it...that I'm aware of. Unless you know some engineer that can re-engineer the servo motor to do this on the stock 20x and 16x lens!!