Bicycle Mechanics - seatpost collar w/cable stop

i'm having a hard time tracking down a 31.8 seatpost collar with a built in cable stop for cantilever brakes. does anyone know anywhere i could pick one of these up? if not, any suggestions on how to run cantilever brakes on a frame with no brazed on cable stops or seatpost bolt? thanks.

What frame is it - and do you have pics?

Current thinking on my part:
- if possible, braze on your own cable stops from an old frame and touch it up; OR
- NOT RECOMMENDED but I've seen it done, drill two holes in the frame and run the cable through that, using the holes as cable stops. Believe it or not, this worked really well, but it was an old steel frame that had had its day so there wasn't much risk attached to the job.

Alternately, grab a hanger off an old Schwinn or other old road bike that used centerpull brakes. It just hangs from the middle part of the seatpost-bolt, the part that's exposed between the clamps. I've got an extra one sitting around and could mail it to you if you need it. But I'm guessing Harris Cyclery has something like this too. Rivendell might have something too. It should work with any regular seat collar that leaves some exposed bolt in the middle.

You need this? goes on the seat collar bolt. http://www.loosescrews.com/index.cgi?d=single&c=Cable/Casing&sc=Hangers,%20Rear&tc=&item_id=TK-1266A1&id=324068624240

Link doesn't work for me. Here's two links to hangers that connect to the seat collar bolt, from Loose Screws: #1 (http://www.loosescrews.com/index.cgi?d=single&c=Cable/Casing&sc=Hangers,%20Rear&tc=&item_id=DC-B1268&id=458500315684) and #2 (http://www.loosescrews.com/index.cgi?d=single&c=Cable/Casing&sc=Hangers,%20Rear&tc=&item_id=TK-1266A1&id=458500315684).

Nashbar sells the one without the screw for $.99. I have both of those. They're made for fat road-type bolts. They didn't work well on my Trek 930 mtb with a skinny quick release. I ended up using a vintage MAFAC hanger. It hangs down lower, so I can run my cable below the quick release.

thanks all for the help. i think i am gonna pick up one of those hangers. my only concern is the way i picture it sitting in the center of the collar bolt i imagine it wouldn't be too secure. wouldn't there be movement, or would the tension of the cable hold it in place?

There would be some side-to-side movement, but it doesn't matter, because the tension of the cable (b/c the springs in the brakes) will hold it in place. It shouldn't make any noise even if it does move slightly, too.