I use this play pen for my 3 month old puppy
http://www.petco.com/product/102107/...o-Pet-Pen.aspx. He can't climb over it nor get stuck, it's portable, it has a removable waterproof bottom that can be cleaned incase he potties in it but he doesn't, you can unzip and roll up the side if you want him to be able to go in and out when you're home, it comes with a carrying case, and it has an attached pocket to store some of his stuff
I also have little dog gates for him when he's in the kitchen, but at night he sleeps in his play pen (he likes it better than his crate).
Desiree & Eros