I've bought my Philips Xtreme Power bulbs from Strauss Auto -- an autoparts store here in the Northeast. They typically cost $50 for a package of two. Don't think you can buy just one. I love the bulbs because they're so much brighter than the normal brightness OEM halogens. But as you've probably read, they don't last very long (none of the bright halogen bulbs last as long as the normal brightness halogens). My first set lasted about 10,000 miles.
I think Tideland Prius and usbseawolf2000 bought their Xtreme Power bulbs from powerbulbs.com
