Rep panerai ferr has not been made for a long time, and I'm not sure if I can find a good rep rubber for him in the same design.
I would check Ali and Ebay, and if not, I would put a standard pam rubber tunnel, from the same sources, or check with TD about the availability.
Fortunately, there is more choice in this design.
Do not forget to just check with the seller that you are looking for a buckle strap, not buckles, because rubber straps for them have a different width of the fastening cutout and are thinner at the ends.