10mm may be a good solution. My RIA 10mm is a heck of a gun. The round is the same diameter as a .40 S&W and can be double stacked like a .40 and still keep the grip size relatively small. Also, if the .10mm were selected maybe ammo would be easier to find. Admittedly, Ive never done or read any comparisons between 10mm and .45ACP terminal performance.
If memory serves; 10mm is the semi-auto equivalent to the .41 magnum. The .40 S&W is a de-tuned 10 mm to match the .45 loaded with 185 gr. at 850 to 900 fps (to remain sub sonic). Military issue .45 is 230 gr. at 850 - 900 fps. Extrapolating the numbers without the tables I’d say the 10 mm is a step up in power from the .45. I still prefer the .45 in non combat scenarios to reduce the chance of over penetration and maximize energy transfer to the target.