Warning!
You cannot use a headset cable stop with suspension. You NEED to get the stop from RockShox or another company that mounts to your fork crown.
The reason being, if you use the headset stop, the effective length of the cable will change as the fork lowers move through their suspension travel. As you compress the fork, you'll create slack in the cable, i.e. no stopping!
Try sending RS an e-mail directly, or try to do a search on the web for bike parts. There was a company that specializes in small misc. parts for bikes, but I can't remember the name of the company. Maybe someone out there knows it. Try posting this in the "Bicycle Mechanics" thread.
If you can't find one, you may be forced to switch to linear pulls (V-Brakes)
Good Luck!
L8R
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger