Perhaps investigating the Association of Balloon and Airship Constructors will meet your needs. Larger models, of course, can be built, but probably not much larger than this. (If you're a modeler, please check out that last link, frustrating though the photos are. And may I further say that the N-M URL is the assiest URL of all time.)
Your Zep: Buy it or Build it? My wife pointed out that Nieman-Marcus has kindly made the opportunity to own a Zeppelin NT available to the, er, masses. Others, however, offer more modest means to airship ownership.