I have a wide foot, so my go-to styles won't help you (though I've been on a similiar quest to replace a pair of black sandals I own that are falling apart for a whole year with no luck!!). BUT, my mom has a narrow foot, lives in FL and only wears sandals. This is her latest pair and they looked dressier than I would have guessed by the photo (and super cute) if you can stand the toe thing.
http://www.zappos.com/merrell-stella...fcTest=fcl%3A2

If the toe thing is not your style, these might work too (I tend to prefer slides):
http://www.zappos.com/merrell-shudra...fcTest=fcl%3A2

Both styles come in multiple colors.