Well, if you are looking to upgrade your seating then perhaps this will help - and only costs about $175. If you need entirely new seats, then perhaps this information may be of help to others...
Take a look at Ebay - there are some 350Z custom made synthetic leather seat covers that are OEM stitched and custome cut, one for ABS seats, and another for non-ABS seats. They come in a variety of colors, both mono and two-tone. I think the two tone with black and silver are the best....
Here is the link for the seat covers:
http://cgi.ebay.com/ebaymotors...ZWDVW
If you want higher grade real leather OEM fit chk these out:
http://cgi.ebay.com/ebaymotors...ZWDVW
Best of luck...
Chris