Here's one I designed as my first electronics project: https://github.com/tadfisher/nyx-kb https://github.com/tadfisher/nyx-kb Seems to meet your criteria, but

Here's one I designed as my first electronics project: https://github.com/tadfisher/nyx-kb https://github.com/tadfisher/nyx-kb Seems to meet your criteria, but obviously requires some assembly.