The folks Rivendell have been preaching 650B wheeled bike for a few years now, but the Bombadil (pictured below) is their first offering in the MTB realm. Obviously its steel, and lugged. Both very items in the cycle world, but its stuck in the past with its 1" headtube. I would assume it will be offered with the matching fork, as its will be pretty much the only option, unless you're getting a fork custom build. Still, its a pretty neat bike and i'm sure they'll sell a few. Retail price sits at $1,500.
(NOTE: I'm not sure what tires are mounted below, but they looks narrower than Pacenti's Neo-Moto, perhaps whis could be a 650B that will easily fit your standard 26" MTB frame.)