On my last Hilux, I used the rims and tires (they are sort of integrated) from Tamiya's 1:32 motorized Wild Willys Jeep. They are only as tall as the Aoshima's Swampers, but they are 1.5x the width. Otherwise, there's not much else out there that I know of. Check the toys at Wallyworld, you might find what you're looking for on a cheap diecast.