Love the start button. Plan to do one on mine too. So far, I bought an OEM one that's the same as my Scat Pack. Will know later if I can make it work. Which one did you go with? Looks like maybe Viper or Viper truck?
I measured all I could find, the best fit was from a Honda S2000. Most of them are larger. The button was an option on the keyless entry / ignition system I purchased.