Comment by fleaaa

Glove80 is a decent ready-made product but it's simply too big. From my experience, sofle/silakka/lily58 with tenting solution worked better since they have smaller thumb cluster and surface but still takes advantage of same structure.

The ones I listed are well open sourced and modularized, you can print out parts as you go - trackpad, trackball, tilting pad, joystick whatever you want.