MVMNT is an independent, family owned dance studio/creative space dedicated to the representation and preservation of urban arts & artists, teaching break dance, house dance, and capoeira.
Stop by MVMNT in Berkeley and ask if they know anyone. I've only been there once (to pick up a friend's kid), but it is a wonderfully welcoming space that teaches breakdancing classes, among other things. The people there are great connectors, so I bet they know someone who can mentor a budding beatboxer. Good luck with your search. Here's a link for MVMNT: http://www.mvmnt.co/breakin