Hello,
I recently purchased some 2009/2010 Vibe GT wheels for my 2010 1.8L Base Vibe. I've been search for the correct type of lug nuts to mount these to my car, after some searching online (GenVibe included), and purchasing a single GT lug nut from a GM Dealer I have finally found what seems to be the OEM equivalent lug nut.
The dimensions and type of lug nut can be seen on the White Knight website:
http://www.whtknight.com/cgi-bin/item.cfm?subcat=77
I ended up buying the 73138TXL (made by Gorilla Automotive Products) on Amazon. Here is a link to Gorilla's website:
http://gorilla-auto.com/lug-nuts-page-14
Also, thanks to keithvibe for the excellent photo of the two different lug nut styles on the Pontiac Vibe here:
viewtopic.php?t=34366
Let me know if I am incorrect about any of this, but mostly I hope this helps out others.