So far as I know, the most accurate 9mms are the Berettas developed by the U.S. Army Marksmanship Unit many years ago now. They spent a lot of time, money and science determining how to make the service pistol that replaced the 1911 accurate enough for NRA bullseye shooting and other competitions. They ended up with pistols that are capable of putting ten shots into less than 1.5 inches at fifty yards, and with the right hollow point ammunition much less than that. One unusual thing about them is that the twist of the barrel is half that of regular 9mms. This was a significant step to improve accuracy.
Comparable guns are sold by David Sams Custom Gunworks. Very expensive, built to order and it takes about a year to get one. But you asked!