The AutoHelm wheel pilots are supposed to be able to work with a GPS to follow a course. You will need the very hard to find interface box to put between the controller and the GPS. I found such a box, but no instructions. I'm still trying to figure out the correct combination of wires to connect and buttons to push to make that feature work. I'll get there eventually.
But in the meantime, just having the wheel pilot hold a course for me works very well.
FWIW - I've found the best way to locate some of these hard to find items is to use Google Alerts. I was able to find that rare interface box and the elusive SL 555 Sea Tiger manual winch with this method. It may take months before you get a hit. But eventually, someone, somewhere in the world is going to post a "for sale" for the item you want. And Google will find it and notify you.