You absolutely cannot go wrong with Book of the Righteous. I've substituted its pantheon for the Core D&D pantheon in my current campaign, and shucks howdy do my players love it.
You can add Mystic Eye Games' The Pantheon and Pagan Faiths to the list. Also, coming out in Q2 this year will be Bastion's long-delayed Lore of the Gods. This is one book that seriously rocks.
I suggest Faith & Pantheons, which contains a lot about the FR deities. You can pick any number of those deities and add them to your existing world with little or no effort.