Thanks Fox
Assuming that it is a Track Control Arm that you need, and not a Compression/Banana arm, then I have these here: http://www.ebay.co.uk/itm/Nissan-350Z-Front-Lower-Track-Control-Arm-Wishbone-O-S-Right-Driver-/281958702143?ssPageName=STRK:MESE:IT
Used but fine.
If it's a compression arm you need then, I would try ZManAlex for used, failing that Ebay for a cheap new copy version, or Nissan for the genuine expensive full fat new version.
Thanks
Jon