I tried this with coil springs, but didn't really work. I think there is too much friction at the shaft to enable it to turn smoothly.If you can't find one, you can make one. Get a rotary switch with a long shaft, add a collar to the shaft behind the front panel using a long screw in place of the original set screw. This long screw will work against a leaf spring blade to return the switch to its original position, two blades on either side for a center-off position. You will problaby have to disable the detent portion of the switch to lower the turning force so the springs can work properly. Alternatively, you could use coil springs in mounts in place of the leaf springs.
Price is a bit steep, but not a problem. The style and US location, however, are.