I can't use one as I have way too many trees to work around. I also can't point you to anything tractor specific. But These are great multi use umbrellas with mounts. I use them on my bass boat and in my canoes. They are designed to be folded up by the wind without breaking. $35 or so with the mounts at BPS. They also sell the mounts separate. I always thought one would be great on the tractor.
Umbrella is 60" in diameter. Pretty much just a durable golf umbrella with a mount for the handle.