I am not sure if you are aware of the company "Sensory Comforts"? It sells a cushioned-type seat which provides a rocking-type motion. It is portable and designed for use when one needs to be sitting in a stationary position for long durations. I understand that it is especially beneficial for schooled children; but I imagine that working environments could be similarly constrained.
Pat
ETA: http://www.sensorycomfort.com/