Letter for Sponsorship

I am need to find how to write a generic sponsorship letter. My club, West Indian Cultural Club, is a club in Baruch College. We are having our annual Caribbean Show along with two other clubs-Caribbean Students Association and Table Tennis Club. This letter would be sent to many companies, public and private organizations. The show will be held in the school's Mason Hall on May 7th. If someone could help me with this, it would be great and a load off my shoulders. Thanks a million