John D.,
Do a search here for "3-stop Eagle in G". I posted it May 19th, 2012.

You all know about a reed-manufactory in the Czech Republic named Harmonikas. Link#2.
The make Helicon Bass Reeds by request.
They also make reedplates for Bayan, Bandoneon, .....
Maybe it's also possible to ask them to make reeds that looks/sounds a lot like the Old Germans.
Just a thought.