What replacement bulb can I use for my 2005 Chevy Equinox's rear side marker lamp?

I am having a hard time finding the replacement bulb for my rear side lamp (according to the manual). The manual states the front one is bulb number 168 but the rear is W5W, which I can't find in store or online. Can I use the 168 as well in the back or do I need to go to a Chevy dealership? I don't want to over pay for a simple bulb.|||http://www.donsbulbs.com/cgi-bin/r/b.pl/鈥?/a> You can get your bulb on the site posted.Even my chevy dealerships parts dept has been having a hard time getting these bulbs from the factory.Some of the newer style bulbs are getting harder to find.Ive used the site posted for lots of special bulbs for friends and family.Best of luck.|||take the bulb to your parts store and match it