This may be possible if in the East Bay region if you connect Oakland with San Jose. I'll post any (likely horrendously grotesque looking) updates.
Something along I-880 and I-80 would probably work.
Probably can't be done for the Bay Area;
there aren't enough plurality/majority black areas between Richmond and Oakland to get over 19% or so. But if anyone wants to prove me wrong, be my guest.
I managed to get a South Central LAX-
Compton-
Torrance-
Long Beach-Cerritos-
Westminster district that's
28.5% Black, 28.4% Asian, and 9.7% Non-Hispanic White. This version completely bypasses downtown LA, and it makes more sense to draw an Inglewood + Long Beach district than an Inglewood + Alhambra one.
It's hard not only because so much of LA County is majority/plurality Mexican, but also because the various Asian-heavy suburbs are far from each other and tend to have a lot of White and/or Latino residents. Long Beach having a lot of super-diverse precincts doesn't help when you're trying to draw a district that's <10% White haha.