I seem to remember reading that almost all the buyers and (hopefully all for this one) sellers of nuclear weapons on the black market are from western intelligence agencies. So, yeah, I think we are spending money on this sort of thing. We also have standing offers to rebuy stingers, IIRC.

A better question is the funding for securing nuclear material in the former Soviet Union. It seems to disappear and reappear periodically in Bush's budgets. I don't know what the situation is in the most current budget proposals.