if one cluster bomb filled with nerve agent is enough to kill
thousands (a weapon of mass destruction) then how hard is it to find a
six foot long by 2 feet diameter cluster bomb in a huge country like
Iraq?  I mean what are the chances of finding one - statistically
speaking of course...and does it factor in that it may be hidden in a
place so no one finds it?

How can this be answered accurately?  The "bomb" could be buried 50
feet under ground and hence entirely undetectable if a building was
then constructed above it, or even hoisted in a tree in the middle of
a forest - presuming Iraq has forests.

Any expression of the "odds of finding a weapon" would surely be useless?

You don't want to know the odds?  The chances?  Saddam used them
before so we know he had them, but where?  What are the chances?