Storage Options / Rear Floorboard of the DC

I am a little disappointed with myself for not hauling more than I do, but my most common freight are the youngsters who each occupy a car seat in the back. I have the seats permanently in the down position because removing and reinstalling car seats in the DC is a pain if you have never tried it.

What I do have is a lot of unused space below their feet on the floorboard across the width of the cab. They are many years from being able to touch the floor, hence I would like to utilize this unused space. I am not a fan of putting anything in the bed for security purposes. Has anyone seen or are using a storage container of some kind that sits on the floorboard in front of the rear seat?