It's always good to have a stock supply of different screws, washers, bolts, nuts, clamps, etc. upon etc. especially if you own a car or house.
That kind of stuff just builds up over time. I'll try to look up the specific screw for you, but I'm lazy and I would have to log out of this screen to get to my other and dig around in the PDF Celica manual then log back into here. Maybe by tomorrow. Good luck.