Keep an eye on the For Sale/Wanted Forum. I lucked out and scored a full set of brand new OEM lug nuts from a member for about $25.00. I scored a second set from a local member in exchange for some universal-type lug nuts I had.
FYI, the steel wheel/wheel cover-specific lug nuts are the same on all 2003-2010 Vibes. Also, the GM part number is:
#88972746. Worst case scenario, you may want to check out the price for a full set on
GMPartsCenter.net. They offer good discounts on their GM parts compared to dealer prices and they also offer free shipping (although you do pay an $8.95 handling fee).