[Bike...and Dennis]

What makes you think you need one? I'd be willing to bet more than 50% of those installed weren't needed.
And, replacing the stator is probably easier than altering the bike for any car alternator kit.

 

[Bike...and Dennis]

I've looked into the series regulators and can't find anything designed and made for this bike. They all require relocating the unit and rewiring the bike's charging system.

 

[Bike...and Dennis]

I honestly don't know. However, the units I've seen don't use the same plugs, and won't fit in the stock location.

 

[Bike...and Dennis]

John, that link is a dead end.

 

[Bike...and Dennis]

Yup, there's plenty of room in an Airstream. .