Yazmin's exercise pen is 36" tall but since I use it in my in back yard, I found a Cover on eBay that will protect her from birds, cats or any other creature that could possibly get in her pen.
I'm sure it would would work for your purpose also.
I usually put her in the pen while I'm doing yard work so I don't have to worry about her slipping out the back yard while the gate to my fence is open.
24 30 36 42 48" Dog Exercise 8 Pen Fence Create Cover | eBay