Welcome to the forum Mark! 
I've been using an old (as in 40-50 years) set of car chains on mine. They were originally my dads that I later used on my cars a few times. They are worn to the point I lost the nerve to run them on the road years ago. They almost wrap around the tire twice. I use the regular catch to hold them tight and wire to hold the remaining loose end.
Got to be careful with the wire though and wrap it so it does not punch into the sidewall.
If memory serves the last car tire I had them on was a E78-14. I don't know what the metric equivalent is to that off hand. (Maybe around 195/70-14? ) My Deere's tires are 20 X 10 - 8 Super Turf. One of these years I will get around to cutting them down to the correct length. 
I only use the tractor for occasional towing of a trailer of firewood. I don't plow or snow blow with it though.
I've been using an old (as in 40-50 years) set of car chains on mine. They were originally my dads that I later used on my cars a few times. They are worn to the point I lost the nerve to run them on the road years ago. They almost wrap around the tire twice. I use the regular catch to hold them tight and wire to hold the remaining loose end.
I only use the tractor for occasional towing of a trailer of firewood. I don't plow or snow blow with it though.