MAGINELS Pet Playpen Puppy Crate Kennel Rabbit Fence Panels Exercise Pen Cage Yard Large Portable Foldable for Small Animals Rat https://www.amazon.com/dp/B0781JFDVJ/ref=cm_sw_r_cp_api_i_JTMTJAKQZ9C7V0CDC6MZ?_encoding=UTF8&psc=1

These are what i use, you can use as many panels are you need to make it the right size, i ended up buying two sets of them to get the pen as big as i want it