Closest I can come is the Kahr PM9. There is a high-dollar option slightly smaller, IIRC (Rhorbaugh), but reports mention some reliability problems.
But as for "one gun".....I don't think horsepower is as much an issue as "shootability". I'm not entirely against having a pocket pistol for when it's needed, but I'd hate to have to limit myself to that alone.
You might consider having a tailor modify your pockets, or just wear clothes with bigger pockets.
