The Washington, DC, metro area is very fortunate to have leading teachers in almost any art you could want. You would be in proximity to the city of DC and southern Maryland in addition to Northern Virginia, so expanding your search may locate the Okinawan style you desire. A lot of Marines at Quantico have trained while stationed in Okinawa, so you may want to ask around at the base. They also have a thriving MMA culture there.
With regard to other Japanese styles -- Aikido is a very prominent art in the area because it was Mitsugi Saotome's first stop after leaving Japan. He founded the still-thriving Ueshiba School located in Takoma Park, Maryland. There is also an Okinawan-style aikido school located in Woodley Park, DC, of which I cannot remember the name but was impressed with the teacher.
Or, if you have an interest in samurai weaponry, there is the Washington Area Budokai, located near Old Town Alexandria in Virginia.
Quite honestly, I haven't heard one bad thing about any Japanese style dojo in the area. I would recommend visiting several and finding out what you like.
Hope this helps, and maybe we'll run into each other sometime!
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