My little Papillon is an escape artist too. I tried a couple of pens and she figured a way out. THIS works
Purchase the Iris 8-Panel Pet Pen at Walmart.com. Save money. Live better.
You can also get extra panels. They fit together with rods and you can change the size and shape easily. You can also use two panels to block off doors/halls. It is easy to move around but too heavy for them to get under. Works great outside too. You can screw the locks closed, good thing because mine learned to flip them.
Shop around for the best prices but make sure you are looking at this one that is 34" high. They do make a shorter one.