Made the clip to take a 3.0mm x 35mm wood self tapping screw with countersunk head.
Printed in black PLA, but anything should work.
I used 4 walls and 5 top and bottom layers with 40% infill.
Added the Fusion 360 file for those wanting to adapt it to suit their needs.
Note:
Be careful when removing the old / broken clip as the folks at the Unicord assemply line decided to use a ~40mm long nail with harse deformations (one way ring shank) to retain the nail in the board. The nail will pull out some of the sisal fibers, but that's not a worry as the screw can be used to push most back before screwing it down.
The author marked this model as their own original creation.