We often connect ours via USB C to a powerbank. It just has to have enough output, i.e. one that could also charge a laptop.

we charge the integrated battery of the projector with a powerbank,

Yes, this works with a PD-capable power bank.
The projector then draws approx. 3A at 19v and can even be operated in brightest mode (which is not possible with the internal battery).

Yeah. You can use a Powebank for that.