If the clip you are looking for is roughly 1/2" wide by about 1 1/2 to 2" long black stamped metal clip you might try locating a MotorMite inventory of fastners/repop parts at your local Napa, Pep Boys, or Independent Auto Parts Stores. Some of these odd parts are in the bins that are in the stores but when you ask the counter guys, they don't know they're in their inventory BC they are not usual parts that guys are looking for.
Also try Frank's Pontiac Parts at this link:
http://www.frankspontiacparts.com/
Good luck!