Portable / stand-up air conditioner (Yardley, PA)

We are in need of an ac unit that we can use as a supplement in our house on very hot days. We have one portable ac unit that we use in the kids' room and we would like another to use when our parents are visiting, or downstairs during true heat waves. We keep the windows open most of the time so ideally we are in search of a portable or stand-up unit that can be removed easily when not in use.