I swear every time I bring gear with me while traveling, I still only end up using my laptop and headphones. The best travel controller I’ve found is the Sensel Morph: https://sensel.com/pages/the-sensel-morph
I end up using that as it provides a MIDI keyboard, an MPE keyboard, drum pads, and control dials. It’s great for me, as I can use it to test practically anything on our products if I’m away from my main setup. I can also recommend the Faderfox UC4 as a great, small MIDI controller, but I’ve never travelled with it.
My current favorite travel buddy is TidalCycles. It barely uses any battery, and it’s nice to use only my keyboard when I’m on a cramped plane. I’ve made it through four hour flights with only that, whereas something like Max, Ableton, or Bitwig will burn my battery down in 1.5-2 hours tops.