MidWest Homes for Pets Folding Metal Dog Exercise Pen, Indoor/Outdoor Playpen with Door, 16 Sq Feet of Play Space, 42-Inches Tall, Gold Zinc

It is best to just use a tall metal xpen that doesn't have a paint coating. Something like this one. If you purchase two sets you can make a nice 4x6 or 4x8 pen with it and use any remaining panels as a gate for another room (or whatever you like). Plastic will always get chewed, as will wood. Metal is the only permanent answer with buns.