The cheapest option would probably be a pop-up crate, but I don't know if those come in a size large enough for Ivan. They also have no real structure, so if your dog is even the slightest bit naughty, they might roll the crate like a hamster ball. =P
N2N are the ones I like but they are not cheap. Target and Wal-Mart have some generic ones but I doubt they are going to be big enough...