We bought an AIS transceiver for our Raymarine C80 plotter and we are very pleased. We got the same unit that is West Marine branded ($500) but was being sold directly by a company called Cactus Marine who imported them from England where they are made. We got it at the Annapolis show and don't remember the price but it was a lot less than $500 and is a transceiver.
Install went fine. It requires a particular baud rate setting on the chartplotter and that might be a problem if you are sending data at other rates to other devices because it seemed to me that you could only have one baud rate sent - but I willingly admit to not being an expert about electronics.
Finished the circumnavigation in early February in Grenada. Have to work on a book project for the next several months so the boat will be waiting for next year.