What is the GM or (preferably) Toyota part number for the 4 10 mm screws that hold the radio unit in? I've found out the hard way that it isn't Toyota part # 90159-A0010 which are too big. It's for an '08 Vibe.
It would probably be easier to take one of them to home depot or an electronics store and compare them and see what they have... that or fish around corollas/matrix/vibes at the junkyard...Belated welcome to GenVibe, BTW!!!