Here is an OpenSCAD script to generate a simple wall mounted charger holder for the Oral B IO 3 toothbrush. It may fit other models but I have not tried. It is fixed to the wall or other object using a single screw.

I looked at a few designs and there was a common theme that the charger base is retained in the holder. I wanted a holder that would allow easy removal when going away on holiday and be wall mounted. There is a large hole to facilitate removal of the charger if required.

I've only printed one of these so your milage may vary. Mine was printed in while PLA+. I printed mine upside down and required supports for the inside but this is covered by the charger when in use