The link is to the absolute biggest puppy pen I could find for our giant pup.
View attachment 2240750
NOT the bloodhound obviously but you can see its size in relation to the sofa arm.
Each panel is about 2'wide x35"tall.
Ours has been through 2 giant puppies now. I don't like the tiny door so I pull a connection pin and open the whole panel.
Another option.....not as portable.....is to build a giant brooder with wire and 2x2 lumber.
View attachment 2240751
This is my starter brooder....just 2'x4' and 2' tall. Thing is when building one you can customize the size.