Barkingdog,

check out Kopps bike shop in Princeton (you did say
central NJ right?).
They may not have a large selection of used
but I'm guessing they can point you in right direction.
Englishtown Auction?
There used to be a good LBS in Highland Park but
I don't remember the name (on the main drag to the
bridge into New Brunswick). Also its getting towards
summer, college letting out, you might check the
college papers to see whats available.

Marty