Bernie has learned how to jump out of the expen.

This would be fine if he was able to use the pee pads or hold it when he has to go. But, he's still a puppy. So I guess I have a couple of options and I thought I'd get your advice.
I can:
a) get a larger (taller) expen
b) see if there are "lids" or covers for the expen.
c) other options...?
What do you think?