How do I find sponsors for a startup business?

First things first: You need a business plan that will show anyone who loans or invests money what they will get in return.  Generally, by actually writing the plan you will come across the mistakes or holes in some of your thinking.

Then it's about getting a group of advisors and professionals to look over your plan.  Then and only then are you ready to go looking for money.  Too often people go see the "people with money" before they are ready and wonder why they are not taken seriously.  It's only after you have put in serious effort that people will take your idea seriously.

A great book on this subject is by Keith Cunningham, called Keys to the Vault.