How do I write a letter to local businesses for donations of baskets/goodies?

How do I write a letter to local businesses for donations of baskets/goodies for our 135th Alumni Banquet in June 2010. We are looking for baskets/goodies for "basket raffle". Our alumni ociation is a non profit organization, and we have tax exemption EIN # - shall we add it on the letter too? I need help writing one up.