GPIO Stacking Header for Pi A+/B+/Pi 2/Pi 3 [Extra-long 2x20 Pins] : ID 2223 : $2.50 : Adafruit Industries, Unique & fun DIY electronics and kits
4 different types of 2x20pins Header 0.1'' Pitch for Raspberry Pi A+ P
PiBorg | 40-Pin Female Header
Amazon.com: 2 x 20 (40 Pin) Extra Tall Female 0.1 Inch Pitch Stacking Header Compatible with Raspberry Pi A+/B+/Pi 2/Pi 3 Extra Tall Header (Pack of 8) : Electronics