Isn't there a pretty good homebrew store in SF? also the oakbarrel. I bet either one will let you buy 2 oz here and there as you say
Breaking this into parts... yes, there is a LHBS in SF. (Oak Barrel, over in Berkeley, is a good store, but it's hard for me to get to when it's open.) Yes, the SF LHBS will build a recipe from the ground up, which is a real plus. Sometimes I shop there...for a variety of reasons, sometimes I don't.