I'd suggest looking at handle bar extenders. They clamp on and most could probably be modified to fit a seat tube. I moved a twist shifter from the end of the bars down to the stem using one extender (they usually are sold in pairs). I shortened the tube so it just was long enough to mount the shifter and snapped in the plastic end cap that came with them for a clean look. Ive seen them in black, brushed and polished aluminum.
Norm, of Venice Motorbikes suggested using a glass door knob in place of the one that comes with the shifter. That would add an element of class.
Tom
