I think I've found a source for the o-ring on the adjuster on Campy brakes. McMaster-Carr sells o-rings that are very close in size to the Campy ones (although I think the Campy version is metric) 5/8" OD and 1/8" thick for about $8.00 for 25. I'll let you know how they work.
David Goerndt
Orlando, FL