Peter,
Is the issue with the plastic LAN connector, or a snug fit of the LAN cable in the soft rubber gasket. If it is the LAN cable fit, what is the diameter of the LAN cable, with bend protection, insulator? Is there a LAN cable part number we can get the dimensions for on the web?
Also note that the tighter the fit of the LAN cable in the gasket the better the water seal should be.
Regards,
Dennis