Buy one of these seat covers on Amazon and it will be cool and do a great job of covering your ripped seat. Buy two of them and you'll have a spare and free shipping. All that for less than 1/10th the price NH wants for a seat and a lot more comfortable. I have one on my TC45D and it takes the Texas heat well. It's been on 3 years and is only a bit faded, but still strong and with little wear. It has pockets behind the seat for 'stuff' too.
I second the seat cover recommendation. Have had one on my TC18 seat for a couple of years now and I wouldn't want to be without it. Much more comfortable. Got one for my Mother's Kubota lawn tractor as well.