Does the Raymarine e120 have BNC or RCA video inputs? If so, just about any security analog camera would work. All you would need is coax cable between the display and the camera and a 24-48vdc power supply.
Some MFD's support IP cameras, and there are numerous IP camera protocols. Check your manual or plotter for connector types. If it is Ethernet connected, then it should be able to work with some IP cameras.
Your manual should show what it works with...
SeeVee: I wouldn't want any camera that didn't allow for local access. Since it is a boat and most boats don't have full-time IP access, server-based cameras don't make sense. the reason why they don't make sense is that they don't work without Internet access and secondly, they require a constant IP data bandwidth pipe to send a continuous video feed to the remote server.
My favorite camera company is Mobotix, but they are not the low dollar vendor... they don't require a central server, but can do local or remote storage and have complete autonomy and can send or save video in the event of a video motion detection.