I was able to get new ones sent to me directly from Sanger. Just call them up, they know that the material was a bad design. I got mine for free, but I did buy a $400 bimini at the same time.
In order to change them out, be aware that the old ones unscrew. There is a caulk that they have used on the threads that make them very difficult to remove. I used a dremmel, being very careful to not hit the threads on the tank, then I pealed the fitting out once the center of the fitting was removed.