JC Whitney to the rescue:
http://www.jcwhitney.com/autoparts/P...014316/c-10111
The other option that is a bit more pricey are the German made MEFO MFE 99 tires:
http://www.angelfire.com/ut/moab/parts_frames.html
Mefo tires can go 10-12,000 MILES on a KLR so they should be good for 25K on a GY. Less weight, less power should equal longer life.