Number One fans my be interested in picking up a three part comic series Star Trek: Romulans: Schism, published by IDW. It's a short story detailing the Romulan-Klingon alliance of the 23rd century, from the POV of all three involved sides. Picking up from events of TOS: The Enterprise Incident, Number One is a central character, but now as a Commodore commanding the U.S.S. Yorktown. All three issues have been released and it was a limited run, but such limited series are often collected into trade paperback compilations typically available through retailers such as Amazon.