Resurrecting this old thread, because I'm interested in it too.

the Gocycle seems to have what you're looking for: http://www.youtube.com/watch?v=TPLX_...eature=related

Here's a design that bends the handlebars down the middle, much like the Strida: http://www.youtube.com/watch?v=ISWQAR3aw8o (He isn't manufacturing them yet, so far as I know).