Re: Is there a good flat analog stick replacement for the PS
The older, and now the newer style (from the Asuka version up) PS3 sticks are a 10k type, it's only those with the 4 leads that are a Hall Sensor type that can't easily be messed with. They can be used in place of the 3 leg 10k style if you want to add in an Op-Amp between them, and they can be swapped out for the 3 leg style or Sliders if you just bypass that op-amp mess and go right to the MCU.
About the smallest stick with a button is going to be the PS3 style ones. As far as Sliders go, you could mount some SMT style tact switch under one, but that will mean mounting the slider in some sort of channel so it can move up/down. It may not be as accurate when the slider is moved to the limits and pressed, as it will be off center of the switch then, but it's doable with a bit of work.