Powered water heaters anodes are a specialty item and as of February 2015 are available only from specialty hardware stores and online parts retailers. One such hardware parts retailer, Water Heater Rescue, offers a standard powered water heater anode for $233.
Another online retailer, Water Connection, lists a powered water heater anode for sale without a price. Water Heater Rescue offers a an extended version of its powered anode as well as an installation kit. Powered water heater anodes cost more than the more common magnesium water heater anodes. They also eliminate the rotten egg odor that some magnesium water heater anodes cause as they age.