Weatherstrip
 

Where can I get the black plastic rivets that anchor the weatherstrip to the rear hatch door?

I'm almost positive they don't sell them separately and you have to buy the ridiculously expensive weatherstripping which will include them:
http://www.courtesyparts.com/350z-pa...5_867_868.html

I would try the salvage yards if I were you, they pop right off.

Found the proper plastic rivets at my local True Value store, lots cheaper than the whole weather strip and better than a salvage yard which understandably couldn't be bothered with such a small transaction.