Amazon.com: Ardest 9V Battery Clip with 2.1 x 5.5 mm Male DC Power Plug Center-Positive Barrel Jack for Arduino(Pack of 5) : Electronics
9V PP3 Battery Clip Lead to 2.1mm DC Connector – ETC Educational Technology Connection (HK) Ltd
9V battery clip with 5.5mm/2.1mm plug | Adafruit ADA80 | Core Electronics Australia
Battery Plug Converter - 9V battery clip to Barrel (2.1 x 5.5 mm) - Custom Pedal Boards
Chanzon 9v Battery Clip with 2.1x5.5mm Female DC Connector I-Type Plastic Holder and UL Wire Pack of 5pcs kit for Arduino,LED Strip: Amazon.co.uk: Electronics & Photo
9V battery clips to DC barrel | Prop Scenery Lights