This hot shoe (or actually cold shoe) is a hot shoe splitter which will allow you to connect up to 3 hot shoe items onto one hot shoe connection.
It is sized in such a way that you could fit 3 Sennheiser EW-112 G4 on a single hot shoe mount.
What you need:
An M2 2cm with a ring and bolt.
Pause the print at layer 78 (0.25mm layer height) and insert the nut.
Print at 100% infill you need the strenght to hold 3 items.
Depending on the hot shoe to fit you could make the foot a bit higher. (and thus stronger) but with my current thickness I had no problems.
The author hasn't provided the model origin yet.