i wish i had an answer for you, as i have a jumper too!! i got a mesh ex-pen with a top, but she tore a hole in the mesh door and escaped!!
until i figure something else out, she goes in her kennel when i leave....
i hear there are metal ex-pens with tops, but i haven't seen them myself.... i did get a suggestion to use a fitted sheet on top, but it didn't work for me....