Chuck Levin's Music Center on the Maryland side should have some Bogners, Friedmans, Diezels, and Fryettes. Looks like they have some "Murphy Lab" Gibsons, whatever that is. Probably your best bet.
Action Music in Falls Church VA usually has some older Marshall heads and cabs. Atomic Music in Maryland is a fun place with shit just everywhere and some of it is really cool, but you kinda never know what will be in there.