Back in the days when I had a job, my concealed carry gun for many years was a SIG P239 in .40 S&W. I carried it inside my waistband when I wore a jacket or an untucked shirt (although I can't really remember wearing an untucked shirt very often!
), and I carried it on my ankle more often.
That gun is totally reliable. Nothing less is worth considering.
It shoots an excellent cartridge, and holds an adequate capacity.
It is very accurate and easy to shoot well. I always qualified at least at Expert, and once in a while shot Distinguished Expert.
It is easy to carry comfortably and easy to conceal.
Eventually I bought a second one because it worked so well for me. I had committed to the SIG operating system long ago, so I may have missed other excellent choices, but I never felt the need to go shopping. The P239 for concealed carry, a P226 when concealment wasn't necessary, and the controls were always in the same place, the trigger pull was always familiar.