GPIO Hammer Headers - Solderless Raspberry Pi Connectors [Male + Female + Installation Jig] : ID 3413 : $6.50 : Adafruit Industries, Unique & fun DIY electronics and kits
Amazon.com: Micro Connectors Raspberry Pi 40-pin GPIO 1 to 2 Expansion Board (RAS-GP02),Green : Electronics
Micro Connectors RAS-GP02 Raspberry Pi 40-pin GPIO 1 to 2 Expansion Board - Newegg.com
Female GPIO connector 40 pins - jammastar.com
40pin Gpio Connector 2x20-pin(40pin) Extra Tall Female Stacking Header For Raspberry Pi A+ Pi Model B+ Pi 2 3 4b W/ Acrylic Base - Pc Hardware Cables & Adapters - AliExpress