There is also this one on Amazon. I made one similar from foam-board, cut to size to fit my window width. Total cost was less then $5. Then, used it as a flap, with strong tape across the bottom, and light low tack on the sides and top. I would keep it flapped down with hose attached(my hobby space is dedicated room), until needed, then open the window, pull the flap up into place, press the tape down, then paint. When down, pull the flap down, and close the window.