Ask Moparmarks. He is a member on this site and has access to lots of stuff at his and other salvage yards in Colorado. If he has something it won't be perfectly rust free, but it will be way better than anything available here in the East.
I'm working on a '64 Polara convertible myself, so I definitely 'feel your pain.' I was able to buy AMD sheetmetal for my floorpan work, and I'm pleased with the quality and fit of their stuff. But AMD doesn't offer anything for the Cowl for my car, and the vendor who does have a few pieces for it leaves alot to be desired IMHO.