Dealership may still have them, might try rockauto,com, jcwhiteny.com, then go to used through wrecking online or local. Might also try a local bodyshop and see if they could point you in the right direction.

It would be nice if a company like LMC trucks would put out an import line of truck products.

Until you find replacement rubber, try lubing up the channel, otherwise you could end up stripping the window crank gears. I wouldn't use a automotive type of lube due to the smell, hand lotion or a vegetable oil based cooking spray should work and not create any noxious fumes.