You can actually buy what appears to be the same kit H-D sells, but cheaper, from the aftermarket. Someone posted a link to the company about a year or so back, maybe a search will find it.
I've got the H-D system that came with my SEEG, and between us girls I'd much rather use a spare transmitter for my garage door opener and forget about the H-D system. I found the H-D system cut down the range on all the transmitters, even those in my cars, and they even mention that possibility in the instructions and recommend mounting the H-D receiver more than 25 feet from the opener. I guess that's OK if you have a really wide garage, but my standard two car won't allow that much spacing and still have the receiver near the door for the best signal.
With a fairing bike, get a spare transmitter for your garage door opener, open it up and solder a couple wires to the circuit board switch circuit, seal it up to keep moisture out, and attach it to the inner fairing like the H-D unit. Run the wires to a momentary push button switch that you could mount to the inner fairing or any other place you desire. Mount the transmitter so you can easily get to the battery compartment for that once every 5 years replacement, and you don't even need to rig up a power feed from the bike. I managed to do it on a Dyna many years ago, so it shouldn't be hard at all on a fairing bike.
Jerry