you're talking about coilovers that offer fork type rears for z32 rear knuckles right?
most high end coilovers offer them upon ordering, just make sure you specify.
As far as entry level coilovers, I know companies like KTS and Tein also offer them (except tein basics). Good luck trying to buy the fork housing separately though, I already had a close friend literally BEG tein just to sell him the rear forks for his tein super drifts... but they wouldn't budge
http://splparts.com/main4/part...t.htm