MK IV wiper switch

Anyone know where to source a wiper switch or have an exploded diagram. Actually only missing the piece that shuts the system off.

Here is a diagram of the wiper switch:


Similar problem here- took me 20 minutes to work out that the contacts are prised apart in the parked position by a collar ( missing) so therefore ‘off’ and default is ‘on’ when blades are on windscreen
If you find the replacement part( presuming rubber or ceramic) would be interested as would like to try get mine to work as well

Here are some photos of the wiper contact and insulator bush/collar in place (from my 1948 MK IV 1 1/2 litre):

Looking at my spare parts manual I think the Spindle assembly for the drivers side (which has the contact switch) is Jaguar part No: 734201. I suspect this included the insulated bush attached as there is no separate part number quoted.