I don't think I have Mafac Racers on hand, but I do have Weinmann's (which are functionally equivalent and period correct, more or less).
Meaning, they are no tthe exact calipers that came with that bike, but will be direct bolt-on replacements.
Let me know.
__________________
"Love is not the dying moan of a distant violin, it’s the triumphant twang of a bedspring."
S. J. Perelman