I very much agree with Motokai that your best bet for pulling this off would be to organize it through Harley-Davidson, let them sponsor the temporary import and possibly even some of your travel. The PR value to their campaign of building respect for the brand and for recreational (vis a vis agricultural) motorcycling would be enormous, as this ride could attract huge media coverage.

I'll PM you a name to contact, and if you'd like I can make an introduction.

I enjoyed the videos of your transcontinental ride! You aren't one of those legendary British "eccentrics" are you?

Good Luck!