how to use capacitive touch keypad without using CapacitiveSensor.h Library
Here's one: Microchip mtch6102, though it might be a little more complex than you're looking for.  All the others I found with a quick search were surface mount or single button controllers.  You might be able to multiplex a single button controller like the Atmel AT42QT1011, but I don't know what the settling or reset times are.  It may take to long to change pads, reset the chip, then wait for settling/calibration time (if any).