in Bennington Vermont is the Hemmings museum (free) that has a Isetta
and in Lincoln New Hampshire is a small collection on Rt112 with a crosley, a robin reliant and a nash or 2 inside.
in the Saratoga Auto museum in Sarataoga Springs, NY is a Playboy and i don't think that it counts, but an Amphicar.
those from the top of my head in my recent travels.
Dan in Syracuse.. a VW friend of microcars.