I have never understood the problems people have with seat covers. Do none of you have doormats? Or use placemats on the dining room table? Or have a mat in the trunk? I mean, I'm not one of those people who covers their furniture or stair steps in clear vinyl, but sure, having a little protection is a benefit in keeping dirt off the nice stuff.
Anyways, OP - I use a cheap ($20) synthetic black one-size fits most cover from Cabela's. I have the black one and it fits snugly enough when I need to cover the seat from going to the gym, beach etc.
When date night comes along I whip the cover off and have very nice clean seats.