DEWALT 20V MAX Battery Adapter Kit, 18V to 20V, 2 Batteries and Charger Included (DCA2203C) - Amazon.com
Amazon.com: JJXNDO for Dewalt 20V to 18V Battery Adapter, 2-Pack DM18D Upgraded Version DCA1820 Converter for Dewalt 18V/20V & for Milwaukee M18 18V Battery to Work for Dewalt 18V Nicad & NiMh
Dewalt DCA1820 slide on lithium battery to old post style ni cad battery adaptor | eBay
Milwaukee Battery Adapter to DeWalt – Power Tools Adapters
DEWALT DCB230C 20V Battery Pack and charger combo - DCB230C