Commander 5000 chimney - replacement rain cap?

I moved into a home this past year which has a Commander 5000 chimney. It is approximately 15 years old. Although I would love to replace the entire setup, I don't have the money just now. In the mean time, however, I was wondering if anyone knew of a universal rain cap that I could use to replace my existing one (it appears quite abused). I've called around several stores and everyone says they are not familiar with the Commander 5000 chimney, nor know of any universal rain caps that would fit properly.

Any advice would be great.
Thanks!

bump..