For a playpen you can either purchase or build a playpen. I would suggest making one as it is much cheaper and can be big or small. You can buy a dog/puppy playpen online or at a petstore. These tend to be expense and they are usually very hard to clean. These two YouTube channels did an amazing job on making them and I would suggested checking them out!
DIY Playpen:
https://youtu.be/owtibCd-ygA
https://youtu.be/6d2eUTe2vC8