Finally I found the time to build a solder fume extractor for the "production" place in the lab:
The window insert is made out of plywood and lined with pipe insulation to give a tight fit against the walls around it. Mounted to it are two handles for easy insertion and removal of the insert, and a fan I had laying around (there is a hole in the wood behind that fan, obviously). From that, a plastic air duct can be hung from the ceiling, or just be laid down on the desk. This generates enough suction to allow comfortable soldering while catching about all the flux vapors that arise.