Where do you purchase extended life coolant/concentrate in Socal?

The post with "Gooch's Radiator Flush Procedure" seems to suggest the following products are popular brands: International's Fleetrite ELC, Shell Rotella ELC, CAT ELC, Chevron Delo ELC, Peak Final Charge, Prestone Heavy Duty ELC, Zerex Extreme Heavy Duty, etc.

When I went online to two auto parts stores (with the initials PB and AZ), I didn't see the above brands/products as available.