This subject seems to surface on occasion so I am hopefully providing a little more clarity.
The only difference between the "Criterium" and "Prestige" front derailleur is the front clamp plate and the button cover. All of the other parts are identical. In the 1974 French Simplex catalog the "Criterium" is described and translated loosely "....same as......presentation luxe (deluxe)" meaning that it had a chromed front mounting plate and an alloy cover button vs the "Prestige" which had a nickel (?) plated mounting plate and a red plastic cover button with the Simplex "S" logo. Attached is a link to a photo for those appreciate visuals.
So, if you have a cracked Delrin body on your "Criterium" you can buy a "Prestige" (usually much less expensive) and swap your clamp plate and button.
Jay "one who enjoys visuals" Dubiel Halifax, VA USA