That's the headlight washer jet cover/location.
Send a PM to zmanalex, Shades RS, Clark Motorsport or R35LEE would be probably the best bet for it secondhand.
Links;
http://www.350z-uk.com/user/9648-zmanalex/
http://www.350z-uk.com/forum/207-clark-motorsport/
http://www.350z-uk.com/topic/87886-53-nissan-350z-gt-breaking-spares-with-20-khans/
http://www.350z-uk.com/topic/63996-2004-350z-breaking-all-parts/