I found the URL...this page is for the model best suited to a
vanagon: http://www.swampy.net/t154page.html

It is $267, shipping included.  Sounds great....I called the
distributor.  the only down side...and it is a problem...is the
current draw.  Low speed draws 39. amps, medium draws 7.6 and high
13.9.

I think I will be ok in the desert with my solar charger since I
will likely not use it more that a couple of hours a day...but
still...i bet 4 hours of use would all but kill my optimus.