DEWALT 18V-20V Battery Adapter DCA1820 from DEWALT - Acme Tools
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 20V MAX Battery Adapter Kit, 18V to 20V, 2 Batteries and Charger Included (DCA2203C) - Amazon.com