Anything 3D/dished like the Advantage isn't going to be very portable, just because of the bulk. I suspect many DIY versions are also fairly delicate, as a result of the 3D printing process.

For a flat, split keyboard you could look for one where someone has already designed a case that goes some way to protecting the keys, or make such a case yourself. I wouldn't choose something with this few keys, but [2] is on the first page of the Reddit, and shows what I mean -- unlike the keyboards where the "case" is just a sheet of acrylic, this one looks like it would be OK stuffed in a bag. Many of these keyboards use a Pro Micro controller, which is known to have a weak USB port. Using a wireless keyboard, or choosing a different controller, might also help.

You will have far more options if you're able to solder the components onto the PCB yourself. Otherwise, there are a few companies like falba.tech that sell assembled keyboards.

[1] https://www.reddit.com/r/ErgoMechKeyboards/

[2] https://www.reddit.com/r/ErgoMechKeyboards/comments/ir7axv/a...