Hello otq09398, I hope that I have not come too late! I have just managed to successfully install Sierra 10.12.2 and am also using the Netgear A6100 USB adapter. After doing some googling on the chipset, I discovered this cached webpage with the following info regarding the adapter:
It appears it shares a chipset with an Edimax product. After searching for Edimax's drivers, I found that they DID in fact have an up-to-date MacOS driver for the EW-7811UTC. I've installed it with success on Sierra 10.12.2 on my Hackintosh. It can be found on this page, along with drivers for Windows and previous versions of MacOS. Here is the link to the MacOS 10.12 (Sierra) driver. I've also attached the Zip file and listed two mirrors, in case the Edimax page is down, or the driver is removed.
I hope you haven't given up!