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Not exactly the same but this might solve your problem. I am adding a trackball to my dactyl manuform mini so I don’t need to switch between the keyboard and the mouse on my right hand.

It might be faster to train your off hand to mouse than to train it to do all the typing.

It's intended for people who only have one working hand / arm.

The company also make keyboards for people with no working hands.

https://www.maltron.com/store/p24/Maltron_Head%2FMouth_Stick...

I'm right-handed and use my left hand for mousing. I originally swapped so I wasn't having to move my hand over the number pad to get to and from the keyboard. I don't use a keyboard with a number pad any more, but I've stuck with it. It's quick to learn.