I find the best place to find parts like ground effects is an auto wrecker. While you will see the occasional smashed car or waste of metal (honda civic), you should find at least 6 early ninties cavalers with decent panels. The ground effects should just screw off.
a 2nd gen has 2 phases 88-90 and 91-94
you can fit the 88-90 rear bumper on a 91-94 if you use longer bolts in the back. the same with the side skirts. but as far as i know the 91-94 bumper will not fit on a 88-90 and you have to remove the crush guard to convert from to Z-24
I installed "89" Z-24 rear bumper and side skirts and a 91-94 front bumper on a 1993 4-door RS
but have recently repaced the frontbumper with the FX Designs Bumper (On the Black Cav)