I used to have a TypeMatrix around 15 years ago and really enjoyed it, but the rubber domes wore out on me. Happy to hear that yours survived that long!
There is a commercial product with big keys in the middle - the Truly Ergonomic, which I got afterwards. The new version has optic switches, and you can reprogram the middle keys. I also had the Cleave and have to say, those switches are damn smooth, but I prefer the layout I set up on my Moonlander.