You can use dog exercise pens too as long as youstay out there with her. I wouldn't recommend an open-top penunless you'll be there the whole time because red tailed hawks, whichare very common in Wisconsin even in cities, can and will carry awayrabbits. So will owls if it's night time.
Don't get the small animal exercise pens that they sell at Walmart andpet stores. Any rabbit worth her veggies can jump one ofthose no problem. Plus they're too small to get any realexercise anyway.
If you want a covered pen like Bunnys_rule63 has, you'll need to makeit. I've never seen one for sale here. Make sureyou use sturdy fencing as rabbits can bite through chicken wire.