I'm surprised at Ducati (Or Brembo?) for still using that farty little bit of plastic to actuate the micro switches.. I thought Noah upgraded from those shortly after doing the Ark?
Moto Rapido do stock them separately but they fall below their minimum postage limit, so you would have to bulk your order up with something else.
Ducati Paddy sells the switch, (about £23) which comes with the little spacer.
info@ducatipaddy.com
www.ducatipaddy.com
The farty bit is 5.2mm diameter rod x 5.2mm long. Apparently a 13/64" ball bearing will do the trick.