Ok, I'd like to revise that. It is conceivable, if unlikely, that they could have obtained a device from Pakistan. But that (1) would be large and unwieldy (not a "suitcase") and (2) would be at most one bomb, not 20.
I agree for the most part. I think Pakistan would be a more likely source, but then we have the problem of them actually moving a large weapon around... which is undoubtedly very difficult. I don't know nuclear physics, so I won't comment too much on the actuality of them having a workable weapon. But, I do know how al Qaida operates... and I know they want one. The complete and utter dismissals I keep reading on this board are almost frightening though, I must say.
I seriously doubt that Pakistan has the level of technology necessary to build a suitcase nuke. AFAIK, only the USA and the Russians ever developed any.