I think Ricks advice on the long neck is probably correct, thought I found my Vega Folk Ranger in a pawn shop. If that doesn't work out I would try for a day in Boston while you're in Vermont/NH. They have several good music stores in the area and ususally a good supply of banjo's.

As for the autoharp, the further south you go the higher the prices, but the better the selection. Just a good knocking plywood box without the chord bars will fetch $50 below the Mason-Dixon. Schimdts will go for up to $600 (special models higher) while custom harps will go for $600 up to a couple of K. While you may get some face time with the banjo, (depending on a bit of luck), your chances for examining several used autoharps at once may be slim, and Elderly's or ebay your best chance. Good Luck!