First of all I want to thank @Nelovy_08 for the model he provided.
I remixed the model since I needed a bracket to hold a shelly plus 1 PM - 2 PM, also gen3, dimmer, i4 (and other shellys with the same shape) with the “plus Add-On”.
The shelly plus Add-On has to be mounted towards the base of the bracket. Diameter of the holes for the screws is 3.5 mm.
Can be printed with PLA using a 0.6 mm nozzle and 0.42 mm layer height (like in the photographs).
Available file formats: .3mf, .f3d, .stl.
The author remixed this model.
See description.