You might be thinking of the 632, a 6-shot J-Frame available with a 3" barrel chambered in Federal .327 Magnum. These had adjustable sights, and a slab-sided barrel, nice piece. I don't see that S&W currently catalogs that model, and they never really took off, so there's not many floating around out there. But if you look, I'm sure one will eventually turn up. This is a good place to start your search.

Failing that, a Colt D-frame of some iteration as mentioned above would work. But, again, they are getting scarce and pricey when the do come up, even more so in a 3" barrel. But they are out there. I saw a 2nd series at my LGS about a month ago.

A final thing to consider is that a 3" revolver is not really a pocket gun. For a belt gun, the new S&W Model 66 with a 2 3/4" barrel should start hitting dealer's shelves some time this summer. It's a 6-shot .357/.38 Special that looks like a winner. Even though I prefer the older ones, I'm seriously considering this one.