Good question! They messed up and didn't get ours ordered with one, but it makes getting in and out so much easier and the added room to put bags is nice, so we don't miss it. We don't even fold up the seats to let people into the third row. They just walk through.
Hopefully someone will know. I'm sure they'd just bolt into place, the question is, do they have them available for order, or do you have to buy all the pieces and assemble?