Hand-operated rear-brake?

I recall having seen a Dax, produced and sold with a hand-operated rear brake.

But which year/country model was it?

I'm thinking about adding such a lever to my Danish ST50/1973 setup, and would like to know where to look for the spares - especially the metal thingy that goes onto the frame.

Anyone who can point me in a sensible direction?

Cheers,
Martin

Pretty sure it was a CT70, early model.
Lots of the z50a 's have this as well, even some of them were equiped wit a front hand brake + rear hand brake + rear foot brake.