Amazon.com: 9 V Battery Clip Connector, I-Type 9 Volt Battery Clip, 9V Battery Buckle Connector Hard Buckle Plastic Housing and Black Red Wires Leads Iength 5.9 inches (I Type Hard Shell 8PCS) :
9V PP3 Battery Clip Lead to 2.1mm DC Connector – ETC Educational Technology Connection (HK) Ltd