Well, welcome! A couple of choices. There is a Paper-Source right in Georgetown. It is more of a paper store than a stamp store but it has some stamps.
If you can get to Tysons, keep driving! Skip Tysons and head out to Reston to Angela's Happy Stamper. Her website is
www.ahappystamper.com it is well worth the ride -- about 20 minutes farther than Tysons.
Have fun. The weather has been awesome but the humidity may be creeping back...