It appears that a serpentine crank pulley from a Nissan SR18 or SR20 may bolt directly to the Fiat twin cam crank. The OE nissan part would include an elastomer for balance, and there are aftermarket pulleys with double elastomer or fluid-filled designs. as well as billet parts of course.
I'd rather convert all of the accessories to serpentine than tack on a serpentine belt for just the supercharger. Buying pulleys that are a bit shallow and shimming them out should be relatively easy.