Goodness me! That dyna is real chewed up!

Its food for the bin I'm afraid, I wouldn't waste any money in getting that repaired. It is exactly how mine was when I purchased my bike. The question is.... how on earth did it get like this? I think that it may have got pretty hot sometime.
Anyhow apart from SRM, another place to get one from is here...
http://www.norbsa02.freeuk.com/goffyelectrex.htmI had just bought one from him and found it to be excellent. You will want to test the field windings though, if they have had it as well then you'll need a new one, but... You'll need a special tool to compress it into the dynamo body, while your at it check the bearings too.
Good luck and let us know how you get on!