Touring bikes are such a specialized niche for dealers and it's hopelessly unrealistic to expect a dealer, even in an area as large as the DC metro area to carry a large variety in multiple sizes. The smaller shops with good service can't afford to stock more too much of bikes that sell slowly and many of the larger shops are mostly slick retailing operations more interested in moving merchandise than helping you get the "perfect" bike.
I currently own both a Long Haul Trucker and an older REI Novara Randonnee. Have owned a Cannondale touring bike as well. I can understand one wanting to get the "right" bike with the correct fit, especially since a good bike isn't inexpensive. However, it's not an easy task and, from my experience, I doubt there's a bike sitting on a showroom floor that will be perfect for you from the moment you sit on it. You may change the handlebars or the stem, probably the seat, maybe even the seatpost (setback or suspension). Factory tires may not be of your liking. If you're picky and willing to pay a bit more, I suggest just finding a frame/wheel size that will work for you in a brand / model that you like and building it up to your specifications.
If you'd like to try out a 58cm Surley LHT equipped with moustache bars and bar end shifters in the DC area, send me a note. I have a couple of friends with different touring bikes and perhaps I can arrange for them to all be in the same location.
As for Mt Airy Bikes, Larry Black has a big inventory of new bikes (particularly unusual and exotic ones) and a huge inventory of used bikes. You can peruse the list of his used bikes on the bike123.com website. Be forewarned that while he has a lot of things, it's not a straightforward go and look at the bikes as he has the bulk of his used inventory warehoused apart from his retail operation. Also, his prices are fair but it's a business and Mt Airy isn't exactly cheap. (I paid several hundred dollars extra for a new recumbent tandem from Mt. Airy because he went out of his way to let me and my partner borrow his personal tandem for test rides. I'm cheap but service is valuable and worth paying for even when the location isn't exactly convenient)
Best of luck to you.