I think there's a guy who sells from a cart outside the store at Belmont and Cali. Not sure he's there past noon. I would also suggest La Casa del Pueblo, but it's further from where you want to go. I'm sure you could find a jimenez, or a tony's at least, or a standard mexican grocer that will have at the very least some "pancho's" products.
We cannot be friends if you do not know the difference between Mayo and Miracle Whip.