Amazon.com: Camco Magnesium Anode Rod for RV, Camper and Trailer Water Heaters - Extends the Life of Your Water Heater by Preventing Corrosion| Fits Atwood Heaters - (11553), Magnesium - 1/2" NPT
8735100873 - Buderus 8735100873 - Magnesium Anode Rod D26 x 505 mm, G1" for the S120
Yamaha 40-60 HP Magnesium Anode Kit For Freshwater Use – Zincs For Boats