Make a ThinkPad Keyboard USB Adapter With Arduino : 5 Steps - Instructables
LotFancy 9.5V AC DC Adapter for Casio Piano Keyboard SA76 SA77 SA46, Replacement for Casio ADE95100LU - Walmart.com
MIDI to USB Cable, USB to MIDI Cable Converter 2 in 1 PC to Synthesizer Music Studio Keyboard Interface Wire Plug Controller Adapter Cord 16 Channels, Supports Computer Laptop Windows and Mac - Walmart.com
Model H: IBM Keyboard USB Conversion - John Hawthorn
Amazon.com: 4x4 Matrix 16 Key Membrane Switch Keypad Keyboard for Arduino & Raspberry Pi (6 Pack) : Electronics