I have a fairly original Ford sunshine Cab 13 tucked away in the shed at home as a future project. There are are no rubber seals the canvas is simply pulled tightly over the roof cutout via an edge rope and cleats. When open the roof is rolled back it is tied to two eyelets that hold the roll at the back curve of the cab roof.
The sunshine cab is a popular restoration item in Australia and a company in Queensland "Blitz'n Bits" sell complete replacement kits for the sunshine roof. I will try to get a contact number for you if you wish to purchace parts