I think for a charging cat the best thing would be a 12ga with buck shot. I know you where looking for a pistol but a shot gun would be less likely to miss.
Shot placement is everything! I would rather take a round of 50BMG to the foot than a 22short to the base of the skull.
all 26 of my guns are 45/70 govt, 357 mag, 22 or 12 ga... I believe in keeping it simple. Wish my wife did as well...