I'm with Puma Guy. If I were going to go with something of a similar ilk I think it would be the Bond Arms Defender...though at 20 ounces net it isn't exactly credit-card size.
On the semi-auto side, there's also the tiny Seecamp LWS 32. A little over half the weight of the Defender derringer but in the slightly anemic .32 ACP. Still, though, in a package only 4.25" overall length and 3.25" tall you get a 6+1 capacity.