Over here this is the type they have mostly as after market cabs. http://www.laurin-inc.com after that it's the Sims Cab which is most common. They make for my Kioti but are pricey, I will make my own next year as I will not go through another winter blowing snow in my face and freezing.
I couldn't find one for a JD 790 anywhere but Sims. At $3,000 plus for a cab with vinyl doors and no heat I gave up and swapped the tractor on something with a factory cab.
I know that probably isn't the answer you're looking for, but I think it turned out to be a good decision. Good a reason as any to get a new tractor!
I have found some all vinyl but they require a canopy. Apprx $1,000 plus the canopy Another $400. No glass so no wiper and no heat, but out of the blowing snow and removable for summer. They were on EBAY