@Cstrock ,
Unfortunately, I've surfed nearly entire web and only found a couple places that sell your requested product, and they are in Germany. Also, while conducting my search, I found several sources that recommended the keel gasket be inspected or even replaced every year, depending on your location and water conditions. Supposedly, the reason for this is the plastic/rubber material the gasket is made of tends to dry out after being moved from water to dry air, and will eventually crack and become stiff overtime. This may prevent the keel from lowering all the way, if at all.