FWIW, getting quality yamadori stock takes a lot of looking around, mostly in-person as well as personal connections. That means getting out and looking at bonsai shows. If I were you and had that kind of cash, I would be eagerly awaiting the
National Bonsai Exhibition in Rochester, NY in September. Bar none, that show will bring the best yamadori vendors all in one place. BC are nice, I have a big one from Cajun myself, but the vendors at that show will have some extremely nice material (Ryan Neal, Andy Smith and a dozen others will be there most likely) that you won't see anywhere else.
BTW, It's unclear exactly what you're looking for--Western conifers are not all that great a choice for the DMV (which BTW for those not living here, stands for the District, Maryland and Virginia--go Nats, go Orioles
). If you spend a considerable sum on a collected Western alpine juniper, ponderosa or whatever pine, you can expect a lot of disappointment, IMO. Too wet and humid in this region to keep them without a lot of hassle. And good luck getting Randy Knight to respond or even acknowledge you.
The best yamadori for here are deciduous and broadleafed eastern natives and landscaping trees, such as elms, yaupon holly, BC, hornbeam, beech, blackhaw, blueberry, boxwood, wisteria, apple, bradford pear, bittersweet, Japanese maples. Given that this area has so many old and extremely old landscaping, there are some extremely nice old JMs in yards that can be great bonsai. Boxwood can also be found at homesites in larger sizes with a lot of rugged character. The twisted old boxwood below was at a historic site in Fairfax county. It was protected because the site is historic, but there are other sites around with such stuff if you have the contacts and know where to look (landscaping companies are your friend). The pic of the bonsai is of a boxwood made from a hedge in Arlington. The raw stock was purchased at a regional club bonsai auction--Potomac Bonsai Society (which includes Maryland clubs) has one most every year up in Beltsville.