Nissan is still showing the parts you need for the calipers available, have you checked any of the follow or locally?
thenismoshop.com
nissanparts.cc
courtesyparts.com
mynismo.com
Nissan Performance Aftermarket Parts | Nismo | Nissan Racing Parts

parts:
440 Front Brake :: Brake :: Genuine Nissan Parts :: 300ZX Parts (Z32) 1990-1996 :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com