You are best advised to modify your craving so that a good Salvadoran chicken noodle soup or Mexican albondigas or Asian noodle soup will suffice. I have worked for over 15 years in Monterey Park in a courthouse filled with lawyers and bench officers who love matzah ball soup and it simply isn't around.
When we're feeling the need, particularly due to sore throat, etc, we find that the Salvador chicken soup at a little shop in the Atlantic Mall (where IHOP is) fills the bill very nicely. I will try to find out the name if you are interested.
There's one option: Danny's Kosher Pickle in Covina.
I haven't been to Billy's, so I couldn't tell you which one to visit if they're equidistant, but Danny's is a lot better than it has to be, considering that it's probably the last chance for anything of the kind before Vegas, at the very least.
It's not Brent's or Langer's, to be sure, but it's better than Jerry's (and probably 1/3 less expensive), and better than Canter's on the latter's bad days. As for Art's (mentioned above), I have NEVER liked it. Ugh.
Danny's Kosher Pickle Rstrnt
326 N Azusa Ave, Covina, CA 91722
Unfortunately no. The Jewish population (or lack thereof) in the SGV isn't big enough to support it. The closest you'll get is Billy's in Glendale, which, in my opinion, is mediocre at best. It certainly is no Brent's or Art's or Langer's.
You'll have to venture to the San Fernando Valley where you have Brent's (the original Northridge location is MUCH better than the newer location in Westlake Village), Art's in Studio City and surprisingly, Jerry's Matzoh Ball Soup is very good. I don't care for too much else at Jerry's but their Matzoh Ball sure hits the spot.