does anyone know where to obtain an off switch for the above b&o the switch has been tested with a multi meter and found to be open circuit on one side i have put an on off switch on mains cable but not really satisfied with this arrangement

Take it out, take it apart, clean the contacts and put it back together.
Or
Take it out and send it to me.
Or
Let me have a look in the dungeons and see if I can find a good used one.

Martin