As requested by BlueMaster27, I have added a main body with fixing lugs and the Sonoff insert included in one stl 'Main Single Entry with insert and fixings.stl' I have also raised the Sonoff up by 1.5mm to make the button protrude through the lid a little.
I just wanted this to have both power cables entering from one end, so that it could be fixed to the side on my Sigma.
I'd suggest using 17-18mm M3 screws for the cable clamp to ensure there is room for both cables.
Id appreciate you posting a make if you print this.
3D Printz UK PLA