'04 Zepplin cracked nose cone

Has anyone had a problem with a cracked noise cone on a Zepplin RV? I have an '04 24' Zepplin II. Last year I found a crack starting at the top and it was 1' long. I drill stopped the crack and covered it with rubber roof material & caulked it. This spring I see it has continued to crack. Is it possible to repair it or do I need a new nose cone. Where might I buy one since this style Zepplin is no longer made?