Just USB

A custom-built USB stick which registers as an HID keyboard to automatically run commands.

Assembly

You can find the 3D model on thingiverse. After printing, simply put the electronics inside the case and snap the parts together.

Name	Amazon DE Price (Price I paid)	AliExpress Price (longer delivery)
Waveshare RP2040-Zero	€11.95	€6.52 ($6.98)
USB to USB C Adapter	€9.56	€0.66 ($0.60)
3D Printed Case	~€0.25	~€0.25 ($0.27)
Total	€21.76	€7.43 ($7.85)

Austrian Prices listed, prices in other countries are usually less

Install CircitPython as described here.
I recommend PyCharm for programming. To upload scripts, simply move them to the drive of the microcontroller.
- Show terminal using sudo chmod 777 /dev/ttyACM0 and screen /dev/ttyACM0 115200 (on Ubuntu)
- Show terminal using screen /dev/tty.usbmodem2101 115200 (on macOS)
Upload setup.py and run it once, then overwrite it with rick_roll.py or auto_password.py
Done! Happy Hacking!

This project is for educational purposes only. I assume no liability for software or hacking damage.