Allow me to quote my own post to you:
"It is simply easier to make it from the more abundant bismuth or lead than to try to separate it from the uranium ore, or to try to separate the 25 isotopes from each other."
For the miniscule amount required - even to have the excess to extend the effective half-life - simply ask the mullahs in Iran to siphon off a little (or do you think they don't know how?). Or that dictator in North Korea, or any other reactor-possessing hostile power you might think would want to see the US hurt (say, France). It really wouldn't be that hard. It is produced for medical and other research. You can order it from Oak Ridge if you have the right credentials.
"For the miniscule amount required - even to have the excess to extend the effective half-life - simply ask the mullahs in Iran to siphon off a little (or do you think they don't know how?). Or that dictator in North Korea, or any other reactor-possessing hostile power you might think would want to see the US hurt (say, France). It really wouldn't be that hard. It is produced for medical and other research. You can order it from Oak Ridge if you have the right credentials." - calenel 
Oak Ridge won't sell enough Po-210 in sum in any 140 day period to make a single atomic trigger, no matter what your credentials.
Iran's reactor isn't working yet; it is a non-entity for all *existing* weapons.
North Korea is grappling with the technical hurdles in making enough Po-210 fast enough for their own nuclear test. Frankly, my money says that Iran will have a successful nuclear test before North Korea and that neither will be able to test this year.
So there's a prediction that you can fact check me on over the next 5 months. I'll be right while you are still in wide-eyed panic.