You'll need to find the panel. I can keep a look out around here for one, but those trucks are few & far between here, to begin with, let alone find one for parts in the wreckers. Chances are that that panel will be easier to find down your way. Don't worry about the condition of the fabric. The heat down there has probably killed most of that on any you'd find, anyhow. The actual panel condition is the important part.
First thing I'd do is get some deadening on the roof first. At least then while a panel is being tracked down, you're AC (yea!!!) will be more efficient & it wont sound like a big ole tin can inside.