Nevonexpress provides Membrane 3x4 Matrix Keypad at lowest price online.
The matrix keypad has 12 buttons, arranged in a grid of 3x4. It is made of a thin, flexible membrane material with an adhesive backing (just remove the newspaper) so you can attach it to nearly anything. The keys are connected into a matrix, and that means you only require 7 microcontroller pins (3-columns and 4-rows) to scroll through the pad. Our matrix keypad also includes a 7-pin extra-long header strip so you can plug this into a breadboard with ease.