The best place to buy a college pennant is your school's bookstore. Head down to check out the selection and maybe sell back a few of those old textbooks while you're at it.
If you can't find a pennant at the bookstore, try an online search. There are numerous Web sites catering to your pennant needs, some of which are listed below. Fill out your information and let the pennant come to you.
If you can't get online, try heading to the school library to use the free computers there.