I installed the Richard Franiec grip for Sony RX100; it sticks on with a strong adhesive. Seriously, why didn’t Sony just build in a grip in the first place— the Franiec grip is a big improvement in being able to hold the camera securely. Recommended!
Richard also has grips and other cool stuff for quite a few other compact cameras including the Sigma DP Merrill and Olympus E-PL3 and E-PM1.
Because I use the Really Right Stuff L brackets on my Sigma DP Merrills, I did not opt for the Franiec grip for those, but anyone shooting them handheld would no doubt like the grip on those also.