I checked with Brasseur today. The coupler for the S-2 is not available.
Since only the very end (the upright "T" part) had broken, I was able to hot glue the remainder of the "spring" and the coupler centering function was restored. I am going to install this coupler on the front of the switcher so I don't think it will be used as often as the rear coupler.
As an aside, removing the coupler from the chassis does require separating the halves that contain the motor etc. however the "T" piece comes out much more easily if the metal hanger clip is removed first. That requires the tabs on the metal piece to be straightened and the clip pulled up and out. That frees up room in the slot so the "T" will come out without breaking. To reinstall, the clip is pushed back in and the tabs twisted AFTER the "T" piece has passed thru the slot.
