But you can't type when the laptop is on a laptop stand.
Then you need an external keyboard, mouse and mousepad. At that point you're not far off from just slapping a monitor on the table instead of a laptop stand.
You should look up portable monitors. They are crazy small, cheap and good nowadays.
You can get a 15-16" OLED external display with a battery for around 300 western monetary units. Half that if you stick to IPS panels[0]. You can shove one of those in a backpack easily.
Then you need an external keyboard, mouse and mousepad. At that point you're not far off from just slapping a monitor on the table instead of a laptop stand.