Try Paul Dunn, Tel UK 01782 856839. I got an armature for a D6 from him in December. I know he had a batch re-wound and may have some left. He also does bearings, brushes and the field coil. I have just got mine reassembled and working using a DVR2 (12v) regulator from dynamoregulators.com and it works great.
Cheers
Mark