The ElecFreaks Exclusive Crystal Battery Box for micro:bit (2xAAA) specialized for micro:bit. You can place two AAA batteries into the battery holder, switch on, and then it will supply power to micro:bit via PH2.0 connector.
Note: For a bigger battery box, you can buy 2xAA Battery Holder with cover or 2xAA Battery Holder without Cover.
1 x ElecFreaks Exclusive Crystal Battery Box for micro:bit (2xAAA)