I went for the ‘03-04 Mustang Cobra spoiler from LMR.com ($60). My ‘94 is black, so color wise it matched up well enough. Not sure if you’d be ok with it on your white car. Just did some very simple cut-to-fit with a pair of tin snips, drilled holes for nuts/bolts/washers and viola!
If you want to color match, you might want to go with ttocs idea