Scuf Gaming is the industry leader in high end, competitive controllers. They are used by the vast majority of professional eSports players and are well known for sponsoring some of the largest eSports leagues in the world.
Scuf Gaming has a link to apply for a sponsorship on their website but they don't specify any requirements. The form requests a lot of information including your social links, social following, and any eSports teams you play for or represent.
Each sponsorship is considered on a case-by-case basis and people who are sponsored receive a 5% external discount code and earn some portion of revenue share.