Stuttgart Germans would be WAY too frugal to buy diecast planes. They´d even be too frugal to surf the web.
As for ordering in other parts of the country, their local lingo is about as incomprehensible as Bavarian - they´d never get what they want.
Usually, you can find Herpa models everywhere, and the rest by mail order. I personally prefer ordering from ACB in Berlin when I don´t want to buy overseas - you can pm me for phone # and address if you want, or take a look at
www.aviation-center.de.
See... Kiel Germans are a lot nicer than those from Stuttgart!
If you ever travel to northern Germany during your stay (absolutely recommended!), you can contact me about stores in Hamburg or Hanover - or just to chat or if you have any questions about weird customs around you...