The answer to that is to make your own and hand-solder wire to the switches.
And /r/ErgoMechKeyboards on Reddit is a great community for understanding what you're trying to achieve.
Building a keyboard is tedious, but not particularly difficult.
(I built my first keyboard about 7 years ago as my first foray into 3D modeling and printing. It went well enough that I used it as my main driver until I got a Keyboardio Model 1 years later.)