Gasoholics Anonymous

Searching eBay for "folding bicycles" turns up lots of options.

Foldabikes carries the Brompton bicycle. They also have travel pages extolling the possibility of using a folding bicycle for long distance travel.

West Marine carries a range of folding bicycles, because, well, that would be helpful for a boat owner. For similar reasons RvToyOutlet also has folding bicycles.