I have been trying to find a place to do this as well. The link below lists frame builders who will retrofit your existing frame with S&S Couplers.
Ditto what Owen said. But I'd add that most pro shops have relationships with builders who do S&S. It's not entirely in house, but you can generally handle the drop off and pick up locally and pay the same amount as if you'd sent the frame away for retrofit. Bilenky, for example, works with a number of local shops in this way, effectively offering outsourced coupling services at wholesale.
That reply was from six months ago, but you may be right. Doesn't hurt to call and ask
How did I know Niall started this thread.
i just saw on the Blue City Cycles blog that they do, in fact, do S&S coupling now: