The article you kindly attached says:
"Iodine-131, however, is usually found in water as a dissolved gas, rendering reverse osmosis (which cannot capture gases) an ineffective treatment mode. It can be removed using a combination of relatively simple technologies, though, and personal radiation water filters are available, utilising filtration methods and medias frequently used in the nuclear power industry. The EPA recommends the general public adopt a process combining activated carbon, reverse osmosis and ion exchange – effectively covering all bases."
Not sure if there is a gizmo that utilizes all three processes it mentioned...