In browsing for a keypad, I see they’re all a little bigger than will fit the face of my inclosure. What about all these cell phone keypads. …are they matrix like in their wiring? Or does anyone know of a ‘tiny’ matrix 4x3 kekykpad?
This Keypad - 12 Button - COM-14662 - SparkFun Electronics one is about 2.5", but that includes all the pins and casings. Good Luck!
Why not wire up your own?
Use some of the little tactile switches, a piece of "island of holes" perfboard or similar, make as small as the switches will allow.
The switches in the 2nd row will fit in 0.3" by 0.3" so you could easily fit 16 in a 1.6" x 1.2" rectangle.