What about these guys? It would seem they would move down the 4mm required to adapt, and you would get more power, These can be a little finicky on touring bikes if the wheels go out of adjustment, but mine don't so I would try them. You could ask them what they would recomend and what kind of lever would suit.
That said, 27" wheel are a pretty good choice for touring. Just look up any article on why 29ers are the salvation of the wheeled world and all the same arguments may obtain. Walmart sells a folding Bell tire for them that comes in a number of treads, where you find it, and the smoother ones seem pretty good to me. I was toying with the idea of building a 27" wheel touring bike. I was also like 700C, and 26". So far 650B hasn't called me.