The Rover part numbers are AO 2400 and AO 2401 for right and left hand respectively, the kit is P/No AO 2400 /1K. Rover called them 'drive dogs'.
Sadly long unavailable, even the aftermarket versions.
Some NOS ones do come up on FleaBay, but usually only one side... Let's see if this repost of a missing pic from the other thread works:
That de-registered member's mobile number is still in his profile, if you can see that.