Do you know where I could find a printable online story (that talks about two characters) that I could give to my students to do a compare and contrast activity.

Answer 1

The story depends on the ages of your students.
Have you consulted with your librarian? Surely this question as been asked before. The Fair Education Use allow you to zerox for one time use class sets of short stories. See

http://www.geom.uiuc.edu/events/courses/1996/cmwh/Copyright/ed_fairuse.html