Tomtom GO 910 GPS Receiver "fixation" Questions

...is an empty hole with a screw thread. It appears that this should have an insert in it to make the fixation to the windscreen holder more rigid when it clips on. Can you supply what appears to be

...same one download the manual for it here. Je poss?¨de un 250DX DUAL BEAM, j'ai perdu la sonde et sa fixation en mer pouvez vous m indiquer un revendeur en france pour me procurer les pi?¨ces ...