That's sad - there is no full-line Nikon dealer left in a big city like DC? There are certainly places in the country where that's true, but I would have thought DC would have had at least one dealer for Canon, Nikon, Sony, Fuji and maybe Panasonic and/or Olympus... Boston is down to one real camera store, Hunt's Photo (with a bunch of branches), but their flagship store carries all six of the above plus Fuji Medium Format, Hasselblad (X1D system only) and Leica. I suspect at least one of their other branches would also have a Z7 in stock (the flagship store has several at any given time, plus they rent them). They are fully capable of pulling a Z7, an A7rIII, a GFX (although they didn't have a 50R yet when I was last there) and an X1D down for one to look at... To give an idea of how full-line Hunt's is in Nikon, they generally keep the Nikkor 800 f5.6 and several of the Perspective Control lenses in stock. They have equivalent stock depth in most brands - I'm not sure if their Leica stock is all that deep - maybe only B&H actually stocks the Noctilux! Hunt's is missing the Hasselblad H system, Pentax (they are a Pentax dealer, but stock little if any) and Phase One. We also have a Phase One dealer less than an hour away (a branch of Capture Integration).
Even Vermont, where I lived for many years, has a Nikon/Canon/Sony/Fuji/Olympus/Panasonic/Leica dealer. Their Nikon stock would run through the D850 and Z7, and they would often have a D5 as well. They would certainly have a 70-200 f2.8 (Nikon, Canon and Sony, plus a Sigma in at least one mount) most of the time, and probably a 300 f2.8 Nikkor or Sigma. A 300 f4 PF would be a normal stock item, while the 500 f5.6 PF would be a "maybe". They carry a relatively full line (except some exotics) in all their brands. They would have a good chance of having all of the Sony FF lenses except for the 400 f2.8, many or most of the Canons through the 300 f2.8 and probably all of the Fujinons except the 200 f2. They have full pro-line dealerships in everything - they'd be happy to order an 800mm f5.6 Nikkor or the Canon equivalent, a Leica Noctilux or a Fuji GFX. I recognize that Green Mountain Camera is unusual, maybe even very unusual, for a rural state.
I would expect a big city with a huge press corps like DC to have something like that... Has a place called Pro Photo a few blocks from the White House disappeared? There's also something called District Camera & Imaging with a big picture of a Z7 on their home page. They claim to be a dealer for the big four, although not Olympus or Panasonic...