Single CR2032 / 20mm Coin Cell Battery Holder with Switch : ID 4856 : $0.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Amazon.com: Mini Skater 2 x 3V CR2032 Spring Clip Black Plastic Button Cell Coin Battery Holder Case with 6 Inch Wire Lead ON-Off Switch.(Black,4 Pcs) : Electronics