I prefer not to use disposable batteries for environmental reasons. But with NiMH, a light designed for 3V will be dim, and an LCD will have low contrast. In

I prefer not to use disposable batteries for environmental reasons. But with NiMH, a light designed for 3V will be dim, and an LCD will have low contrast. In that sense, the effective run time is zero, so NiMH is a non-starter. I found some AAA-size LiFePO₄ cells, spacers, and a charger on AliExpress a few years ago.