Rohrbaugh R9S Stealth.
As small as an LCP but shoots 9mm, and is only a couple ounces heavier (still a featherweight).
I mostly carry it in an Uncle Mikes #1 holster IWB, but instead of IWB, I carry it in my right front pocket with the clip over the edge of the pocket so just the grip sticks out a little. It conceals perfectly under any shirt I wear that's not tucked in.
I have an LCP as well, but I really like the "no plastic anywhere" and exceptionally high quality build of the Rohrbaugh. With 9mm, I don't feel undergunned with what easily qualifies as a "mousegun".
The Rohrbaugh is also expensive, but from my experience and perspective, well worth it.
I considered the LWS380, but it's almost as expensive as the Rohrbaugh, nearly impossible to get (over a year waiting list), and I liked the idea of a 9mm over the .380.