As the C120W appears to be a nmea 0183 network device, you will need an AIS with a 0183 output such as the Garmin AIS 600. What is not clear to me is if you can program preferences through a non garmin plotter. The AIS 600 is essentially a black box.
The other option is to add a full function AIS transponder with a nmea 0183 output to go into your C120W. It appears the Icom MA-500TR
will do that. My only minor dislike of Icom in general is there instruction material can be confusing. The online manual indicates a nmea output without specifically listing it as a nmea 0183. So, if your interested, you should call Icom to confirm that it's compatible with the C120W.
I have the Simrad AI50
on my charter boat. It's a stand alone transponder with nmea 0183 & 2000 outputs. Mine isn't networked with my plotters as they're too old. Forgot it has nmea outputs. This unit works very well.