Rainbow Grocery Coop on 14th St in SF has nice dark chocolate malt balls in bulk. But they are expensive, so I only get a few at a time. They also might be too thick on the chocolate for your taste.
One Safeway (I can never remember which it is, either the one at 16th & Potrero or the one in Westlake, I shop at both) also has dark chocolate malt balls in bulk. Not quite as good, nor as expensive as Rainbow. Also possibly too thick on the chocolate, I don’t really remember.
The calories really add up on those things, so they are a very occasional treat for me. Otherwise I could be more specific.
Roddy