Can a Campy rear brake be converted for use as a front brake?
 

I've got a set of Campy Cobalto brakes but the front brake is missing the blue "gem" thingie. I want to use one set of calipers as a front brake of vintage fixed gear bike I've built up. Can I swap out the mounting hardware, or am I better off trying to take the gem off the rear brake and glue it to the front one? I'm a bit concerned that I might break the gem trying to remove it.

Also, what's a set of these brakes worth in decent condition with levers and the white hoods (given that one gem is missing)?

To make the front brake a rear brake, you just swap the bolts. To move the gem from one to the other, you swap the nuts.

I've heard a similar "jewel" is available at craft stores.

Thanks, problem solved.