It’s worth doing a search of the forum, Roger Hulett asked for a 2 brush diagram in Nov 2008 but didn’t get any response. There is also a suggestion that there are errors in the Technicalities (5.1.01) circa 1930 wiring diagram that is also for a 3 brush dynamo.
If you are in the VMCC the ad. for AO Services in the back of the journal looks helpful http://www.aoservices.co.uk .
You may have gathered that I have the same ambition, and with a 2 brush dynamo!
Richard Tann