While there are many similarities within the Minuets, the "experimental" nature of Argosys means that there are often minor differences among coaches that aren't readily explained. The longer I have owned my 6.0 Metre, the more interesting nuances seem to appear. An even greater number of variables appear when the 6.0 Metre Minuets are compared to their predecessor Argosy 20s.
I agree with Kevin's post, quoted above. My Argosy has some strange stuff no one has seen before, and all Airstream can tell me is, "yes, we built it."
I would try a cabinet maker first to see if he can fab something up that would look good and be useful. It is going to be tough to find something like that which has not been destroyed through time and neglect that would actually be "factory" for your Argosy.
Good luck, and let us know how it goes. We all are suckers for progress reports here.