come one!... just add a Neodymium magnet (they are so cheap even boxes of throw away shit from walmart has them) and a coil... and voila! - change as you spin!.... crank chargers for emergency radios and flashlights have been around since before Radio Shack & LED lights ...
given the resistance may reduce the 'spinner' feel a bit.. but that's easily rectified by making the center pushable to switch between spin mode and charge mode AND adding more weight on the 4 corners for high circular momentum... which would feel nice any way