Colin
If you go to
http://wireless-set-no19.trackpads.net#M11 you can down load manuals on the various types of Chorehorse Generators.
I believe the post-war models were practicaly identical to the war time ones but ensure you get a 12 volt version. There were Canadian production models which can be viewed on the above site.
I assume they charged the batteries via Distibution Boards which were also part of the kit.
The post war models do turn up fairly regularly, and Witham Specialist Vehicles had nos examples a few years ago. Stationary Engine magazine in the UK would be a good source to advertise in for a war-time example.