Different expert here.
I see your question has been posted here for a few days, and I believe you "didn't see a solution" offered because there is no "simple solution" to "integrate a transmitter" into an AIS receiver.
What needs to happen, assuming you want to "do it right" is to REPLACE the receiver ONLY with a "Transponder/Transceiver".
I assume from your question that you may be "on a tight budget", but if you were trying to find an AIS transmitter ONLY, to cost of having such a system would probably be about the same or MORE than simply replacing the receiver with a transponder.
You MAY already have all this information, but please let me give you a couple of link that explain the difference between transceiver/transponders and Receiver ONLY systems. The first is "short and sweet", and the second is VERY detailed.
Short & Sweet Link --> Click Here
DETAILED link --> Click here.
NOTE: Since this is really a "safety item" - in most cases, try to get the BEST QUALITY unit for your situation. "Going cheap" could cost you (and your passengers) their life!
Please let me know what you find or if you have any more questions.
Take Good Care & Be Safe Out There, Greg A.