Hi, I've had a little experience with this.
First of all, I'd start with the kids that go to your school. Maybe you could send out a notice asking anyone if they know of a company that would be willing to be a corporate sponsor.
Maybe you have done this, but it's a good idea to have some goals or plans in mind that you can tell them, when they ask.
Your plans could adjust to what company and to what they think they can provide.
Next step would be going to local businesses and asking to contribute to different occassions. For example, a party, have McDonalds donate the punch, or a pizza joint, some pizzas for a discounted cost.
Having a relationship with the business is a big plus when asking for sponsorship.
We had a thing called "Run for the Arts". It was a fundraiser, but with corporate sponsorship and an alliance with a college nearby.
Each month we would have someone in the art world, theater, music, etc, etc come and have a show for the kids. The "Run", was simply running, each lap provided a certain amount of funds from your family and friends. The corporations provided ribbons, drinks, water, t-shirts, and things like that, and of course money.
Good luck. I'm not in it anymore, but if I can be of any more help let me know.