Paul Biller and Carl Dobrin struck for Redbridge.
Blancos boss Joel Holder told JC Sport: "What a win - we showed fantastic strength and character to battle back from 2-1 down to a 3-2 win.
"With the last touch of the game Simon Moses did what he does best with a fantastic lob over the keeper. Queue manic scenes with a Blancos bundle.
"The questions before the game were can we do it on a rainy day in Essex and boy did we respond!"