You could use the barrier I posted about previously made from metal shelving. It can be cut to any height. I did my at only 4', but you can have the home improvement store cut it to any height you need. I would think that 6 feet would be plenty tall. You then can put it together with zip ties. It makes it really easy to move too. You could add a baby gate in the threshold for extra protection.
Here is the picture again. Just remember mine is only 4', but you can easily make it 6 feet or more.
Here is the picture again. Just remember mine is only 4', but you can easily make it 6 feet or more.