I was pretty much in your position about 5 months ago. I would talk to one of the directors at your school. I'm sure they would be able to find a solo for you. Also, I would contact someone from the music department at the college you are auditioning at. They might have some rules or regulations on what pieces you can play. When you find some pieces, choose one that that would best exhibit your skills. They would rather hear you play an easier piece well than a hard piece, fumbling over a bunch of notes. Do you take private lessons? If not, they might be beneficial leading up to your audition. Good luck!