I built a window for the transom over the master bathroom door (well, the doorway. We still don't have a door). I used an old piece of glass from a window that was falling apart. With accurate measurements and a table saw, this really didn't take very long to execute. Just built an open box with door stop moulding along the inside perimeter. Then leaned the glass in, tacked in some glazier's points, and applied glazing putty to the edge. Tooled a clean edge and done!