For the Quest 3 for example, you can get a Bobovr halo strap that has replaceable magnetically connected battery packs. If you have at least two, you can just swap them when one runs out and by the time the second one is empty, the first one is charged.

IIRC Valve is going to release something similar in a couple months & I am sure there will be other accessory developers chiming in as well. :)