I am looking at getting a new bike with hub gears for the spring , something like the Trek Waubesa. One thing that i wanted to do with this bike was swap out the handlebars for bullhorns. I know that the nexus shifter isn't compatible with anything but flat bars.
I was wondering if anyone knew of a mount or stem that allowed you to attach another shorter accessory bar to the steering tube below the fist stem.
The Hubub adapter fits a Nexus shifter onto a road bar-end. I used this on my 8-speed road bike. If your brake lever will clamp on the bar you can have the shifter and the brake. If you are using bar-end brakes with your bullhorns... not so good. The Hubub is a little spendy. I got mine at Harris.
Another way is to hacksaw off a section of a flat bar and mount it with a separate stem as dabac suggested. I think Sheldon tried that one.
If you have a friend that can weld, cut apart two old quill stems and weld the clamps together so you can clamp the extra piece of tubing to the bars and mount the shifter that way. You'd need one clamp the size of the new bars and one the size of the flat bars. Old quill stems are pretty cheap. I've even seen extension things with a clamp on either end that are used for the stoker on a tandem but that might move the shifter too far away.
Don't know anything about this company but here are some of the things for a tandem that might help you.