I've seen the frozen "log" at Restaurant Depot (also in Alexandria near the Eisenhower Ave Metro station). RD is a membership place, but you're probably not interested in that large a quantity anyway unless you're planning a gyro party. Just a point of information, probably.
1032 Hampton Park Blvd, Capitol Heights, MD 20743
I *think* the place on Columbia Pike near Walter Reed sells it. They used to at least sell their skewered meat raw. Atillas.
Charcoal Kabob in Herndon certainly sells uncooked meats of most of what they serve. Kobeda is probably sold there.
2705 Columbia Pike, Arlington, VA 22204