Yamaha turn signal module FOUND!!
 

Good news, the friend I was trying to help with his 2016/7 Yamaha turn signals found a supplier, we installed the new module today and it works perfectly.

Here is the ordering info:
Partzilla.com/Boats.net
Part number 10-GCA-JW112-41-01 (turn signal switch and module)

Note this is a set it contains the turns signal switch and the electronic module, and it appears this is the only way you can get the module. The cost is in the $200 range.

One work of caution for everyone who contacted me about getting this part, make sure the wiring problem that caused the original failure has been fixed before installing the new module.

Congrats! It's satisfying when persistence pays off. I never give up searching for things because more often than not I eventually find it.

Do you happen to have a schematic for hooking it up that you could share?

It plug-in, and apparently the wiring diagram is a Yamaha secret, I even spoke to the factory and couldn't get one.

That's unfortunate. But thanks for the info

Isn’t that aftermarket add on? If so I suspect why not in factory golf cart wiring harness?

All the ones I have seen so far have a Yamaha turn signal stalk and the Yamaha turn signal module, as well as what appears to be a Yamaha cable system As was told (from the factory) this is an ACCESSORY item, therefore the wiring is NOT in my 400 page service manual, and they do not provide the wiring info for accessory items, therefore as far as I could figure it is not available. Also extensive internet searches have not yielded any results. I would love to get one as I could then install a Signal Dynamics unit at about 1/2 the cost of the Yamaha unit.