I have memories of this odd input device. It looked very similar to a regular computer mouse, but the ball was ON TOP. I think they called it a "trackball". Oddly enough, by simply manipulating the ball with one's thumb, you get the same effect as moving the mouse across the desk, but the trackball remained stationary! I do wonder if that might be useful to you, as it could, theoretically, be placed on any surface and work just fine.