Sounds like you might be talking about the fixed part of the binding's anti-friction device. This is the plastic plate that holds in the moving part of the device - the little curved flat bar that slides side to side on the toe piece.
My local shop recently replaced one of these plates that cracked/tore on a 1.5 year old Pivot toe piece. No hassles at all They said that these crack now & again - especially if they are skied hard & that Look always took care of it. Give your local shop a call.
Rossi uses exactly this same toe piece, so if you have no Look dealer handy, try your local Rossi dealer for an equivalent part.
Even if you have to buy the part, for whatever reason, my understanding is that the plate is very cheap & it takes only a few minutes to install.
If your problem is with the main binding body beneath the AFD plate/slider components, you have a bigger problem...