This is a simple, minimal holder for the Explorer Guitar hero controller, could work for other models, but i have not tested.
If you have a model other than the Explorer, the distance between the pegs is 36 mm.
Alternativly you can remix the model to make it fit your needs.

The plate should be large enough to use double sided tape or velcro wallmount from 3M.
If you want to use the screw holes as is, they are 5 mm Ø and the plate is 5 mm thick.

Print with seams set to aligned for peg strength.
I printed with 15% infill in Grid and mine are holding fine.