Nokian makes tires like that. Trelleborg as well. Stay away from the 26.5 tires. They are harder to come by and more expensive.
One thing I don't like about tires like that is how they sit on the rims. Seems like they are about to come off everytime you look at them. They don't have much of a bead. Real bugger to get back onto the rim too when you have a flat.
Take a closer look before you buy.
http://www.nokianheavytyres.us/tyres-for?kayttoalue=12607911&kayttokohde=12607627 | 
Source for flotation tires/rims for spreader?
