Try a mexican market or Jons might have it. I think I used to see it at Smart & Final. Be sure you look in the different sections, sometimes things are not where you think they might be in ethnic markets or regullar markets.
Any market should have it, but it's easy enough to make at home, which is how I've usually had it. Sometimes it's up with the tinned and bottled vegetables. I've also seen it at 99 Ranch in the preserved-foods aisle.