Hmm... how about, you have a relative who's at the doctor/ophthalmologist/having surgery/etc and you have to go pick them up?
Having to meet with your tax accountant is a good one. Or, if it happens to be a local election day, say you have to go vote. (We had a primary here a few days ago, and I went to vote and was therefore late to work... no one minded)
Good luck
