Polonium-210: A pretty good way to horribly murder somebody

The neutron source that one needs is a reactor… The Israeli Negev reactor (even if it is still the 24 MWt one from the 50’s) should have a high enough neutron flux to produce nominal quantities of Po-210. There are also many reactors throughout the world that also could do it, but it would likely be detectable at a facility monitored by the IAEA due to the need for equipment to process the material.