Just go to your local dealer and have them order a pair at the parts desk, if your lucky, and have a dealer like mine they might even have them in stock
Also by going to the dealer you will not have to worry about getting the wrong size
Let me tell ya about 'dealer' tires. I priced a set for my X475 I bought used with bar tires. I wanted the original Carlisle CS Multi Tracs that came on it. I priced thru my dealer $234 PER TIRE I then checked a couple other places which was sort of reasonable as in $130-$164. Then I priced them at an FS store (Farm Service) and got them for $109 per tire which included mounting them. BTW if your wanting the bar or tractor tread tires, the ones mine had on it were made by Titan.