There are vape shops all over SoCal. The only one I know of that's kind of more well known than the others is VapeRev, but they're not that close to West Hollywood.
Maybe you can glance through Yelp and see which ones have particularly large juice bars. Even smaller vape shops around here have 40-50 flavors in their juice bar, so I'd consider a large juice bar something in the 100+ range.
There are tons of boutique juice makers here in SoCal and some of them are quite good. Of course they're pretty pricy and you don't have many options of reordering once you get back home.