CJMCU-Beetle ATMEGA32U4 USB Keyboard Module UART/I2C Interface - FR-01-471
Amazon.com: AITRIP 2PCS for Beetle Virtual Keyboard USB Pro Micro Atmega32U4-AU Module Mini Development Expansion Board for Arduino Leonardo R3 DC 5V I2C : Electronics
Pololu - Arduino Leonardo
KeyBoh Is an Open Source Arduino Leonardo Shield for Making Custom USB Keyboards - Hackster.io
Arduino Leonardo (ATMega32u4) USB Power Button
Turn your ProMicro into a USB Keyboard/Mouse - SparkFun Electronics
Arduino USB HID Keyboard - MitchTech | MitchTech
Amazon.com: hejhncii CJMCU Micro Card Badusb USB Virtual TTF Memory Keyboard ATMEGA32U4-Module for Arduino-Leonardo R3 : Electronics
USB Pedal HID Keyboard With Arduino Leonardo : 9 Steps - Instructables
Pro Micro Beetle Keyboard Usb Atmega32u4 Mini Development Expansion Board Module For Arduino Leonardo R3 16mhz Dc 5v - Integrated Circuits - AliExpress
Arduino AVR C++: Simple USB HID multimedia keyboard based upon standard keyboard class - Stack Overflow