They are published on the Dow Jones New Service. Market on close imbalances used to be great plays in the 90's. They really fizzled out in 2000. Too many people know about them now. Once in a while you will catch a good one. But, it's rare.
Some platforms have the info integrated into it some do not. You can get it off the DJ Newswire but it's easier when you can just have your universe of stocks on a page, boardview, etc. and see the imbalance so you don't have to watch for it. Redi+ for example has this, realtick (I believe) does not.