Just received my new baseplate and grip from Really Right Stuff and thumb rest from Lensmate. I have large hands so these two accessories have transformed the camera handling experience. Fits well within my SnapR-35 too.
The Grip and baseplate are separate items but can be purchased together. Very well designed/machined, the base has access for battery compartment and there's also a vertical plate accessory for side rail mounting as well.
I really like the thumb grip as it has this bit that protects the exposure wheel to keep it from accidentally being turned.
Here are the links... Really Right Stuff - Item Listing Lensmate: Lensmate Fujifilm X100 Thumbrest+
I've been eyeing up that thumbrest for awhile....especially since I've been known to knock the exposure compensation dial a few times. An hour later I'm wondering why all of my shots look over (or under) exposed. Doh!