Great info guys - appreciate it very much.
One of the reasons I posted is like Woody found, if you Google for the Mamiya 2x you get references to a 2xN and a 2x N-2 AND you also get folks (in various forums over the years) indicating that the 2X N will work fine with the 200, despite fact it is not listed on some compatibility charts.
The lack of info out there on Mamiya glass is painful. On the other hand, maybe it's get - helps keep the prices down.. ;>
Woody - thanks for the fleabay check. There are a couple there, have asked one seller re: shipping but they've gone silent.
Bernard:
I use the 200 on a 1Ds2 (for now) with an adapter so I have a bit more latitude on DoF. Gives great results - sharp, nice bokeh, great color.
Now - given that the 2X is non-APO (far as I know anyway), is the optical quality of the 2x appreciably better than that of brand-name DSLR teleconverter -- given what I use the lens on?