nyblcore is...
nyblcore is available for purchase. The assembled version is ready to play, handmade by me. The kit version comes with all the components (battery included!) and instructions on how to solder it together.
more information at the website: nyblcore.com.
nyblcore is open-source, all the code and boards are on my github here.
If you make this device yourself, please consider sponsoring me on github to support my time and effort in this project and to continue to allow me to explore making devices and releasing them as open-source.
of course, you can also support this work by buying the device directly from me.