How to write a request for sponsorship letter for a Baby Food Recipe Book to be written by a small group of mums.

We are just four new mums trying to earn a buck by writing a recipe book full of baby food ideas (6–12mths).
We are going to approach local businesses and people that would be interested in reaching our target audience for sponsorship.
We were wondering if anyone would be able to show us a sample Request for Sponsorship letter or help us to decide what to include in one.