Mittelmeyer, in Germany, makes a drop bar shifter, for Rohloff hubs.
it is bigger so as to slide around the curves
and includes an eccentric like piece to clamp around the bar via setscrews ,
It's ID the OD of a road bar, and leaves a gap to run the brake cable thru .

May be imported from the Manufacturer, direct, see:
http://www.mittelmeyer.de/html/rennlenker.htm

Got one 2nd hand, that's what he did, yet to build it onto a bike..