Gear change spring tension adjusting cup late part number 57-4008.

[boriscross]

On BSA service sheet 27/71 dated, July 71 mention is made of a new spring retaining cup 57-4008 which has now got an eccentric hole in it to allow the gear change return spring tension to be adjusted. The part number 57-4008 is the same as the old non adjustable part. Does anybody know if you can still get the new, adjustable item and if so where from? Cheers