My commute to work is quite long but there is no "sitting" in Tokyo's trains in mornings/evenings so I program on a smartphone. Yes, it's not impossible but it takes time to get used to it.
Would you mind sharing a bit more about how you make it work? Do you have an app? or are you just using the notepad on your phone?
have you ever considered a nanote from donki? I've been using one as a paired terminal and with the right os (debian, no GUI) it stays cool enough and gets good battery, same with the gpd handhelds
I would go for some affordable AR glasses + a one-hand chord keyboard. No need to hold a device in one hand and operate it with another, while standing awkwardly bent down.
I generally just thumb-type on it with the hinge bent at 180°. I have a colleauge who tried the meta AR glasses and found the display smudgey with his 20/20 vision and my quest 3 I found very screen door-y, though I will admit I liked the apple vision pro's display, I have a fair bit of pessimism about the field as a whole atm, but would like to be proven wrong