I printed a few too many, so I have 2 extra printed in yellow TPU.
It is a Caddx Peanut mount to fit normal GoPro base as seen at Caddx Peanut Mount with GoPro connection by McConnellStudios - Thingiverse
It is a nice tight fit on my (2nd) Peanut, after losing my first one while mounted in the Caddx provided mount…
First two people to DM me their address get them.