The vengeance club essentials have some good vocal samples for such thing, and I'm sure that other vengeance and prime loops sample packs have some pretty good samples, but if you can't find what you're looking for, the easiest thing to do would be to record yourself saying something obscure, "Hamburger monster" in this case, and then apply distortion and other general effects, pitch up or down, and modify it to sound how you'd like. Feel free to sample yourself saying what you want or whatever, don't just stick to the obscure stuff. I just mentioned saying something obscure, because, we all know, that's what a lot of dubstep buildups are
(build up, somebody saying something obscure for about 1/2 measure or so, bass drop, repeat, dubstep fuck yeah)