If you are looking for a replacement and want to keep the original look, I can recommend a guy here:
http://www.cbfourclub.de/boerse/756.htm [ Guests cannot view attachments ]
He, roughly translating his ad (below) removes the original selenium diodes and replaces them with a new bridge rectifier, using the original body, complete with new wires and plug.
I can vouch for the rectifier having used one for about 25,000kms.
The regulator I had some problems with; one transistor blew up stranding me in Sudan for a couple of weeks. The replacement has worked well for nearly 10,000km.