Originally Posted by
frantik
10 speeds from the 70s and 80s didn't really have two levers as much as the levers had an extra extension which allowed you to reach it from multiple positions.
They were also very flexible and gave poor to dangerously ineffective braking. It's not for nothing they were commonly called "suicide levers". You don't want those.
As frantik mentioned you could fit "interrupter" levers that are now popular on Cyclocross bikes and they do work well. Here is Nashbar's version:
http://www.nashbar.com/bikes/Product...32_-1___202418
Note these fit 26.0 mm bars and your Treking Bars are 25.4 mm diameter so you would have to shim them.