On Call of Duty World At War, i got sponsered through gamebattles. You need a pretty good record, no disputes, capture card evidence of the games played and you need to prove you can help to premote your sponsors.
I was sponsored my a modded controller company and a headset company. Im not naming them, but they are well respected.
Just keep your record going strong, get your personal gb ranks as high as you can and try to get top pages.