DEWALT 18-Volt to 20-Volt MAX Lithium-Ion Battery Adapter Kit (2-Pack) DCA2203C - The Home Depot
Dewalt 20V Max = 18V Nominally
DEWALT 18-Volt 2-Pack 2.4 Amp-Hour; 2.4 Amp-Hour Nickel Cadmium (Nicd) Power Tool Battery Kit in the Power Tool Batteries & Chargers department at Lowes.com
Use a 20V Battery on Your 18V DeWalt Tools With This Handy Adapter — Construction Junkie