Pictured above, a teardrop trailer designed to be pulled by a motorcycle, by East Coast Trailer Worx.
Australian site, Aussie Teardrops (which is a nicely informative site, even for cocky yanks) explicitly details the history of the teardrop design, and implicitly communicates how this "open-sourced" design has become a world-wild phenomena amongst do-it-yourselfers. Sure the teardrop disappeared from the public eye for a while, but now the construction of these elegant little trailers seems to be becoming something of a cottage industry.
The March/April, 1939 issue of Popular Homecraft ran a story and plans for a teardrop designed and built by Louis Rogers of Pasadena, California in the 1930's for his honeymoon coach. The 8'x4' floor plan was on tongue-and-groove flooring on a pine chassis. Rogers used a Chevrolet front axle with 28" wheels and 1926 Chevrolet rear fenders. Sides and top were enclosed with 1/8" hard pressed board sealed with varnish.
This teardrop slept two and had the raise-up deck lid for the rear kitchenette with ice box and stove. A curtain-enclosed dressing room outside the starboard entry door provided privacy while dressing.
The February, 1940 issue of Popular Mechanics ran a story and plans for a egg-shaped teardrop trailer. It was built on a 1924 Chevrolet Superior front axle with disk wheels from a 1930 Chevrolet.
TinyTears has plans for sale, including what they call the " '36 uni-wheel," a seventy year old design, which you guessed it, has only a single wheel. A uni-wheel design can be more stable for something trailered behind two in-line wheels, particularly if the hitch allows the trailer to mimic the handling of the bike. It might seem like it's pushing it, but I bet you could design a very streamlined version that would handle (and look) like it was made to be following a Vespa.
There is also a good forum for folks interested in building teardrops, Teardrops & Tiny Travel Trailers. There are some plans posted there, as well as a lot of knowledge and experience with this craft.
OK, wow, I've spent like three hours compiling this post. And that's not including the the four hours I spent researchng it before I started. I guess this is a compelling topic, which you can hope to see more about in future days...
For now though, I'm going to leave you with some links to some commericially available teardrops. And because this is the Dragon, there will be a basis to lighter weight campers that can be hauled on a motorcycle or larger scooter...
Hunter Outdoor Products
PT Snoozer (styled and marketed to complement the PT Cruiser.)
East Coast Trailer Worx
Retro Tear Drops (at 350lbs, a nice home away from home for bikers.)
Adventure Tear Drops
Dakkan Mountain Tear Drops
and of course the company that started me on this line of inquiry, British manufacturer Pod Caravans.
A good place to start looking at these quirky, cute campers is Teardrops.net which is just bursting with links to get you going.