I have a pop up laundry hamper for my guys ($3 at Walmart). I open it up, and zip tie an artificial vine to the sides of it. Then, over the opening on the top I put a towel and use clothespins to hold it in place and prevent escapees. I've traveled 4 hours each way to my vet that way. I place them on the floor of the back seat of my SUV, and make sure that the is the perfect amount of space between the back of the seat in front of them, and the bench seat behind them so they don't tip over.