Re: 1/500 stores in Washington DC
I know of no hobby shops any longer in the DC area since the Airplane Superstore at IAD closed shortly after 2001. Occasionally, I used to see a few 1:400 Dragon Wings at a couple of the Hobby USA's. The last time I went back in 2012 they were liquidating the remaining stock and no longer carrying stuff other than a few Skymarks in various scales and stuff you will find at any of the airport gift shops!
If here for an extended period, in mid December there will be a train/transportation show at the Dulles Expo Center in Chantilly Virginia near Udvar Hazy Center and IAD. Executive models is usually there selling 1:500, 1:400, and 1:200 airliners and a mix of military aircraft.