GPIO 1 to 2 Expansion Board 40-pin 2x20 Pins Pin Headers for Raspberry Pi 4B/3B - AliExpress
This Raspberry Pi Pico Hack Unlocks Two Extra "Hidden" GPIO Pins, and Potentially a Couple More - Hackster.io
Amazon.com: waveshare RP2040-One, 4MB Flash MCU Board, USB-A Plug, Pico-Like MCU Board Based On Raspberry Pi RP2040, Dual-Core Arm Cortex M0+ Processor up to 133 MHz, 29 x Multi-Function GPIO Pins :
Using Raspberry Pi GPIO Pins With the RPi.GPIO Python Library
RPI GPIO Expansion Extension Board
Raspberry Pi Zero 2 W Board Kit Power Supply Camera Acylic Case Heatsink Pin | eBay
Raspberry Pi® 4 Model B – Pinout -
how to plug devices using same pins on raspberry pi at the same time? / Raspberry Pi 4 Model B - Stack Overflow