Where can I purchase zinc anode rods for water heaters

I was just looking at them today at Ferguson Enterprises. Google them. They are all across the country.

Zinc rods are actually aluminum rods with a 1/10 portion of the rod being actual zinc. Zinc's only purpose in an anode rod is to reduce the smell of sulfur in the water. Having said that click on ; Water heater Anode Rods (http://www.plumbingstore.com/sacrificial_rods.html) to purchase one.
Good luck, Tom