Many years ago someone on this forum recommended black RTV silicone. A tube was about $5 from the auto parts store. That was ten years ago and although I don't run these a lot, the silicone is still working. The key is 3-4 thin coats allowing the silicone to cure completely between applications. For me this was about 2 days. It took a week, but it was worth it. Just my personal experience. Good luck,
Bob