Reddit reviews Fotodiox Pro Thumb Grip for Mirrorless Digital Cameras (Type-A; Black), fits: Fujifilm X100S, X20, X-E1, X10, Olympus XZ-2 iHS, Panasonic Lumix DMC-LX7, Pentax Q, Olympus PEN E-PM2, E-P3, E-PL2, E-PM1
We found 2 Reddit comments about Fotodiox Pro Thumb Grip for Mirrorless Digital Cameras (Type-A; Black), fits: Fujifilm X100S, X20, X-E1, X10, Olympus XZ-2 iHS, Panasonic Lumix DMC-LX7, Pentax Q, Olympus PEN E-PM2, E-P3, E-PL2, E-PM1. Here are the top ones, ranked by their Reddit score.
Gives a better, more secure grip for less effortConveniently places thumb near the control wheelMade of high-quality metal24-Month Fotodiox Warranty
Consider one of these: http://www.amazon.com/Fotodiox-Mirrorless-Digital-Cameras-Type-A/dp/B00D62VZBW/ref=cm_cr_pr_product_top
I think this is what I bought: https://www.amazon.com/dp/B00D62VZBW