You list your hometown as Seattle, a major metropolitan area. A quick google search produced this book:
http://www.bizjournals.com/bookoflists/seattle/
Who's the leader in your market?
Puget Sound Business Journal (Seattle) Book of Lists provides you with listings of hundreds of the hottest area companies in their fields, by ranking. You'll also receive the names of key decision makers, along with their titles and complete contact information.
Get a copy of the book, perfect your sponsor presentation and
sponsor packet and start making contacts.
NOTE: Almost every major city has a magazine aimed at businesses and they will often do an annual ranking in terms of sales or by industry. These are great resources for where you might start looking for sponsors.