Depending on your budget, I would go with a Kahr PM9, an airweight S&W Model 38, 638, 442, or 642, or a Kel-Tec P3AT.
I own a PM9, a 642, and the P3AT. I feel well-armed with the PM9 and a spare magazine or two stoked w/127-gr SXTs, even as my sole armament. It replaced my PPK and 642 for...