Finding brakes is all about measuring the reach, http://sheldonbrown.com/calipers.html. Measure the reach properly (as per the online link) and find a brake that is designed to work with those specifications.

No easy task to swap out the fork. You can do it but it will cost money (fork plus all the parts that won't move over because they are designed to fit a French bike) and you will need to read up on how to do it.