I used 15" car-light truck chains on the front wheels of my JD 970. I'll betcha' that a set of import car sized chains (13" maybe) would work just fine.
A chat with your parts guy at the dealership couldn't hurt... mine is always givin' me ideas about options (besides payin' for name brand, etc.) for my tractor.
They know that some things you have to have (can't get away from Mother Deere on all parts) and other parts can be had for much less.
Good luck.
AKfish