From what I could gather, pacemakers contain up to 4 curies of Pu-238 which is less than 300mg of pure metal. Enough to poison a few people but nowhere near enough to create WMD considering the effort. Industrial radiation sources, in contrast, typically contains tens and sometimes hundreds of curies of mostly undecayed cobalt or iridium isotopes, and is usually much less guarded.
I wouldn't be enough to kill many people, but if a certain amount (even non-dangerous, like 1µS/h) of radiations were detected in all Manhattan, the panic would cause lasting damages.
Covered in the article, though the author suggests even less Pu.
A supplier could have a few few devices in a warehouse, but nowhere near the numbers described.
> a pacemaker has only around 135 mg, if I did the conversion from curies correctly. Even so, if I were in charge of keeping plutonium out of the wrong hands, I would still worry about this. It does not seem totally out of the realm of possibility that someone could collect 25,000 pacemakers. Opening 25,000 titanium capsules does sound rather tedious.
