Add Recovery Partition to APFS drive?
I'm still open to quicker ways to do this, however, I managed to solve it by running the full High Sierra installer over the drive.

Get the installer from the App Store. You need to use search as it doesn't appear in your Purchase History.

Run the installer - for some reason it insists on doing the Firmware update again, even though that had already been done.  

Note: It says to hold the power button 'until the light flashes or you hear a tone'. Empirically, waiting for the tone is more likely to succeed. Releasing the button when the light flashes isn't guaranteed to work. If you hold for a few seconds after the tone is heard, the machine will automatically boot anyway.

The install took about 45 minutes in total. 

Recovery Partition was restored.

/dev/disk5 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +1000.0 GB  disk5
                                 Physical Store disk3s2
   1:                APFS Volume KickMeHard              498.6 GB   disk5s1
   2:                APFS Volume Preboot                 19.8 MB    disk5s2
   3:                APFS Volume Recovery                515.3 MB   disk5s3
   4:                APFS Volume VM                      20.5 KB    disk5s4