Contact Lenses

OK, so I need to get contact lenses by Thursday night for a Halloween party. Basically, theres no legitimate way for me to do this 1. Becuase I dont have an up to date prescription and 2. even if I did its running aorund -8.25 in both eyes right now which are tough to get your hands on. Can anybody think of anyway of getting some place or website to get me ONE pair of lenses? Ive got an appointment tommorrow morning with an optometrist and I need ot think of a way to get them to give me 1 pair without committing me to buying more or hopefully charging anything at all.

Suggestions welcome.