The Daily Picayune (the New Orleans paper from that time) has a load of stuff about the fight. The July 8, 1889 issue has a long (it took 3 pages to print it when zoomed out almost all the way) article about it, the arrival of Sullivan and Kilrain to Richburg, etc. The July 9 issue has a complete recap of the fight, each round summarized. I haven't read everything (I didn't even print out everything; my card ran out of money).
That article I linked to above mentions that Bat Masterson was the timekeeper for the match. The paper says that W. B. Masterson of Denver was the timekeeper for Kilrain. William Barclay "Bat" Masterson was living in Denver at the time, so it sounds like it really was Bat Masterson. Why do you never hear about that?