Arduino Pro Micro Leonardo compatible 5V 16MHz ATmega32U4
Processor is Atmel Atmega32U4 with 32K Flash program space.
Program / Power from Micro USB socket
or power 5 - 12v (via RAW DC input pin) or MAX 5V (directly into VCC input pin).
Inputs/outputs
Pro Micro has 20 digital outputs input/output (I/O). Each pin allows for current consumption with a maximum voltage of 40mA, which allows direct connection of LEDs with the resistors and controlling other chips. In addition to standard I/O some of the leads also have special functions.
should be able to get for around $5 (£4)