Here, let me save you $50. It's the same principle, just a USB breakout box. But one better - capacitive input instead of just switches (of course, switches work too)
There are definitely dozens of existing solutions for PC use, but the console world has long been protective of their gamepads and generally don't allow arbitrary custom devices to be connected unless they're built by hacking up a "certified" device.
This is, to my knowledge, the first time any major console has officially supported custom input devices. It's annoying that it requires a proprietary bridge device rather than just getting rid of their artificial limits on HID input devices that work fine on Windows 10 on their Windows 10 powered appliance, but I guess it is still progress.