I see it at almost all of the supermarkets that cater to a Latino audience. I don't know where you live, but the Ranch mkt on Adams and Redondo has it, so does the market on Washington just east of Crenshaw.
There are several Belizian Markets in Mid-City Los Angeles that carry it. The last place I got it was at El Rancho Market on Adams near Redondo. It's SO GOOD. It's my second favorite hot sauce behind El Yucateco Green.