If I was stuck with a 10 round limit, 10mm options designed for 10 rounds or less (Don't know about CA availability)
Glock 29SF or a 1911 (Colt, Kimber, Ruger all offer 10mm)
Glock 29 or 1911 is easily concealed under a loose fit shirt.
In before the
incorrect blanket generalization that 10mm overpenetrates, mythbusted:
https://www.youtube.com/watch?v=Y8Q6bEMJHpY