You can actually cut your SIM card. I've done it with my phone as well as my girl's phone. If possible, ask one of your friends with an iPhone to see their sim. Then, cut your SIM card roughly the same shape/size. Any pair of household scissors should work just fine.
A word of advice, cut small bits an pieces off at a time and then try to wedge it in the SIM tray. It's better to work your way bit by bit (as tedious as it is) than to cut a huge chunk off. Try to make sure that gold strip is lined up in the middle of the tray so that it's completely visible. YouTube is also your friend.
The most important thing is to maintain the integrity of the gold strip on the back. I've done it twice with no problems. It took about 10 minutes to get it just right.
If you don't want to do all that, you can wait until morning and go to a cell shop around your way. Those corner stores that double as phone distributors and unlockers are perfect. They typically have SIM cutters that will do it precisely, but some of them try to tax you at like $10 a pop. :x
