On the Sea Sense web page, under warranty, they say: We are leading the Industry once again with Limited Lifetime Warranty on Entire Product Line!*
Here's the link to their page. I'd email them, tell them the problem, and ask them to send the part as part of the warranty coverage.
http://www.seasense.com/products/39/...l/details/2590
If that's your tank, be sure to include their model number or part number.
Their toll free number is 800-282-8725