We use exercise pens, started off with just 2 foot tall pens, was tall enough for the Chihuahuas. Had to go to the 4 foot tall pens when we got a Min Pin. We bought them online. We got the one with doors, DH cut the top part of the wires at the top of the door, making them like a gate. We have one outside compartment in the motor home that is used to store the pens. When we had the Trailer we just put them in the back of the truck.
I know of one campground in our area that doesn't allow exercise pens. I asked why? Their answer was because it makes it hard to mow. Some places we have gone to and we ask about the exercise pens they have responded with oh yes wished more people would use them.