You can charge your scale's battery by plugging the micro-USB cable (or USB-C cable for the Pearl 2021) into any power supply rated with an output of 5 volts and 1 amp.
There are many "fast-charging" power supplies for sale at electronics and grocery stores. These have an output higher than 1 amp and are not suitable for the scale.
Also, the micro-USB cable can only be inserted in one orientation, as demonstrated below. Please make sure to see if it is in the correct orientation before attempting to insert it, as this will damage the USB port on the scale over time. This happens frequently in a cafe environment.
Pearl 2021 and Lunar 2021
The Acaia Pearl 2021 and Lunar 2021 are equipped with charging protection to prevent the battery from charging under high temperatures. It is normal if the scale does not charge when the surface is hot from brewing coffee. The battery charging function will be enabled once the scale has cooled.