Not sure if this will help you, but I just recently put a Tektro inline cross lever on my fixie. It's the only brake and what I did was take a cable from an old mountain bike that had a metal stopper at one end, ran it through the lever, then into the cable housing, then to the brake. The brake works by the cross lever actually pushing the cable housing, causing the brake to close. It works really well. If you need pics let me know.

DT