You're stuck. You can find plenty of the newer style single cabs rust free but that style, like my 92 club cab is much harder to find.

There are three panels in there and they rust from the inside out. I have located a roof for mine, it's not rust free but it's close. I'm going to start the surgery on my truck this summer. I'll take pics and will post a thread either here or at DTR or maybe both.

You could replace your whole cab with a newer style rust free one though. Just be sure to treat it very well so it doesn't rust as well.