That might be solid planks, not veneer. If veneered, it would have solid edge strips to allow the edge treatment that you see. Either way, you will likely need to either get a pro that does marine woodworking, or learn the job yourself. It will probably involve milling the planks and finishing to match the existing. Not necessarily a big job but does requires some woodworking skills. I don’t know of any off-the-shelf solution for that.