It is called a plastic "cable clamp". On the port side you can see a screw on the left of the cable clamp. Those can be found at most any electrical, hardware, or auto parts stores.
What is the issue, as they both seem intact?
In thinking about it and reviewing photos of my old boat it did not have any cable clamps, and it makes me wonder if they were not added in later. The last place you want a penetration is underwater.
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