Try Chris at TOC Parts. He may have a 2nd hand one from Andy Burnes old stock.
He also said he would p/ex 6v for 12v at one stage when I asked.
Broadway Electrical in Essex can also rewind your 6v starter to 12v http://www.broadwayelectrical.co.uk/classic_&_vintage_car_repairs.html – (speak to Rob Rose)
Anonymous