A race can be organized without the assistance of a sponsor but it'll be really difficult without charging the participants a hefty registration fee. So, in order to organize a proper race that doesn't put a serious dent in the pockets of the contestants, you can try and look for sponsors. Find folks that have something to gain from putting their name on your race. Local gyms, high schools, some energy drink brands, etc. are good examples of folks that would be interested in your product.