Pocket .38 Special: Well, perhaps the Ruger LCR-series? Personally, my usual minimum revolver is the SP101. Don’t yet own an LCR.
Pocket .357 Magnum: Ruger SP101, 2.25” barrel, is my personal choice. Kramer Pocket Holster.
Small IWB .357: Ruger SP101, 3” barrel.
Small IWB .41 Mag: “Small?” Hmm. S&W Model 58. I really did carry mine IWB, back in the day, during personal time, when it was my police patrol duty sixgun. In the Eighties, I had more muscle in my shoulders, so, concealment IWB was not a problem. By the early Nineties, I realized that .357 Mag was adequate for antipersonnel usage, and that my hands were not really suited to shooting N-Frames, double-action, due to that long reach to the trigger. (I have Size L hands, but Size M index fingers.)
I did name 20th-Century revolving pistols, but, as I see it, there was nothing magic about the years 2000 and 2001. I am not better-protected by any revolver newer than the Ruger GP100 and SP101.