Assassin of Bhaal Cowl +2 to initiative. Act Three. Sold by Echo of Abazigal in the Murder Tribunal after becoming an Unholy Assassin. Bhaalist Armour +2 to initiative. Act Three. Sold by Echo of ...
We won't put spoilers here, so we'll just say you can buy them from a character named Echo of Abazigal on two conditions. You have to play as the Dark Urge and embrace your urges completely.