There are three views of my custom made vent for the WB Popper.  The fan is usually available at Electronic Surplus stores. This one came from an old Photocopier and was free.  1/8" plexiglas was bent around the fan to form a channel with the lower half cut away to collect the exhaust. Plexiglass was scrap from a glass company and cost $5.00 CDN.

One end had the fan and the other was sealed with a piece of plastic.  A piece of plexiglass was added to the bottom to lift the unit high enough to fit over the popper.  A side piece of plastic was put on the right side to fit into the groove of this particular window. The open portion of the window was covered with a long strip of plexiglass (the attachment hasn't been invented yet, but is coming).  The initial test was successful with the chaff and smoke being drawn through and deposited neatly on the dog who was laying outside the window and who managed to shake it off when he entered the house :-)