If it was just a nut and bolt kind of a thing...then you can check out this place:
Hawaii Nut & Bolt
Its close to Infiniti. Buuutt..if it is a Nissan part (non-nut and bolt) then well...yup...sorta SOL. Get it from Nissan. If you want it done and put back the same way....in the end...you are going to have to get the OEM part...assuming that you need more than just a nut and bolt. Though....it sounds like you already made this assumption. Hang in there, get the part, pay the $$ then just forget about it.