I checked my bike to get the dimensions. It is this:
Bolt: Din912 Socket head cap screw M3, 12mm long (excluding the head)
Screw: Din562 thin square nut M3, 1.8mm thick, 5.5mm square
Have fun
Johannes
@woody65 and others who might be interested: I have uploaded a 3D model for a TQ charger holder to Thingiverse. You can get it here:
https://www.thingiverse.com/thing:6730165
Have fun