Getting the plutonium necessary to construct a nuke is *much* easier to get than uranium. Building the nuke, however, is insanely complicated.
Access to uranium = very hard; construction = very easy
Access to plutonium = fairly easy; construction = insanely hard
Hmm, I would say that access to plutonium is also insanely hard, as it implies that you already have a local nuclear reactor and reprocessing facilities.
The hard part about getting uranium is probably just the logistics of disguising your mining operation as a desalination plant, or some other type of metal mine. And then exporting the semi-manufactured product to a reputable-sounding customer.