JJ-57 it uses a spring, and Soba it costs $100. I have a P-10, P-18, and a couple Puresmoker Icons purchased off the classifieds here. I really like the Icon compromise with size and battery life. When the Slimplicity came out I ordered it on the spot. Like the Icon you can either "pinky" fire or use the palm of your hand which is very comfortable. It's also a great feature with the Simplicity to be able to use both IMR and protected
batteries.