About 8-10 years ago, I subscribed to a service that would send a few e-mails during the final hour of regular trading, stating the imbalances, both from their own sources and then from official exchange sources, with I think the final about 3:40 NY time. Ultimately I decided it was not worth the monthly subscription service. I don't know if those stand-alone services are still available.
For past few months, after abandoning CNBC, which I watched daily for 20+ years, I tried free news service on Interactive Broker. They offer combined news feeds from DJ, Bazinga, and several others.
Oddly, at about 3:30, they have a line with order imbalances. Sometimes that is not shown until 3:40. It was a minor help yesterday, as I was already short, but at 3:30 the imbalance was $3.2 billion to sell side. That is relatively huge, re stated imbalances, as I think prior this week it was 100 - 400 Million, either buy or sell.
In most cases, I assume that the advance orders are for show, but in any event, by 5 minutes before the 4 pm close, the effect is usually over. HOWEVER, even when just 300 million, I think it shows the short-term psychology, & in most cases, the movement for say 3:40 - 3:50 reflects that action. I think at 3:50 final imbalances are posted so traders can counter if they choose.