You can always look into the automotive field when searching for a sponsor, simply because there is a connection to auto racing. However, my advise would be to look to the places you do buisiness with. Is there a place you interact with that you can help promote? Places like restaurants, pest control services, office supply stores, etc. Remember, with sponsorship your job is to promote your sponsor and to find a way to help them. Study who you do buisiness with, prepare a proposal for their needs, and offer them an opportunity to help them out.
Also don't forget sponsorshiphelp.com. They offer several sponsorship kits and information.
Hope this helps!