another addict here...I am also dying to know of other places...
I once saw a 28 CM Kelly in Gold at Annie Creamcheese for $2,000 (what a bargain). This was probably two years ago when her store was in Arlington. She has since moved to Georgetown. I would guess every now and then she gets one in. It's best to call her ahead of time and ask. There is also a dealer of luxury secondhand stuff in NW DC. I forget the name of the place, but she has been noted in articles as being a reseller of authentic Hermes.