Your source is a book written by a dance teacher and a microbiologist my source is an article written by a nuclear safety expert With all respect to the books authors it is not a reliable source in nuclear issues  Buying hundreds of Pocontaining devices cannot be a big problem for a potential nuclear terrorist in any case In other article by Acton Rogers and Zimmerman they write A Briton Dhiren Barot was sentenced to life imprisonment in  for planning to build a dirty bomb out of some  smoke detectors each of which contains a small radioactive source for use in London  is two orders of magnitude more then hundreds   Actually no need to buy small devices Zimmerman says about  Ci of Po thats  times more than  GBq one may get without a strict state control There are air ionizers with sources of as much as  GBq on the market  times the dose Litvinenko was killed by They can be bought by anybody under modest restraints see httpwwwnrcgovreadingrmdoccollectionsnuregsstaffsrnuregpdf  page  there are estimations on the page  that  of GBq air ionizers are produced and distributed annually in the US market   The quoted articles by Zimmerman et al clearly say about danger of illicit use of Pocontaining devices by a group of nuclear terrorists Just due to this Zimmerman propose to restrict the availability of such devices  Other theories suggest that the polonium that killed Litvinenko might have been obtained from an officially tracked commercial supply after it reached its final customer Polonium is commonly used in static eliminators in printing plants photography labs and textile mills In these applications it is bound in extremely small quantities with other metals Extracting the substance from the molds in which these mixtures are made would be difficult because polonium science is quite complicated Priest said But with qualified scientists and the right lab conditions it is possible I can see how they could be used to brew up a dose to kill one person said Peter D Zimmerman a nuclear physicist and professor of science and security at Kings College London It would require very delicate lab work   So I provided you the recent secondary sources by experts which claim that the amount of polonium Litvinenko was poisoned by could be received from nonstatecontrolled supply These opinions should be reflected in the article