I have a Milwaukee 2621-20 sawzall, what battery and charger do I need?

You can use any Milwaukee M18 battery and charger with that tool, links below to both.https://www.toolnut.com/power-tools/cordless-tools/batteries-chargers/batteries.html?manufacturer=Milwaukee&tn_battery_voltage=18+Vhttps://www.toolnut.com/power-tools/cordless-tools/batteries-chargers/chargers.html?manufacturer=Milwaukee&tn_battery_voltage=18+V