Chris , mac here , I think I have a right side regulator, I acquired about $1800 of various spare J30 parts (dirt cheap)from a valued friend - an INFINITI mechanic who moved away from Phx area !
Get the correct part # ( I forget if Fr & Rr LEFT regulators are same? ), gotta sift through storage , I would check , lube , and run it up/down to be sure it's ok.....probably ask $75 ??
You pm me for further back/forth info ?
p.s. they would be FACTORY ......the REAL DEAL