One-handed portable keyboards? (other than Twiddler)

Hi folks!

I already own several Twiddlers and am very familiar with its pros and cons.

I'm writing to see if anyone knows about alternatives. There seems to be no viable commercial one-handed portable keyboards besides Twiddler. I'm very interested in custom projects that anyone knows about.

Specifically, I'm looking to find something like the Twiddler but with a controller that is QMK compatible. My current project is bumping up against the limitations of the TekGear firmware and TekGear provides no help in writing custom firmware.

Also, for anyone inclined to comment, I'm weighing the choice of spending the time to bootstrap custom Twiddler firmware vs crafting a Twiddler like device from scratch.

The chipset on the Twiddler is: