2 layers21.6 × 52.3 mm

Ps2 pico hat
No0ne/ps2x2pico
USB keyboard/mouse to PS/2 interface converter using a Raspberry Pi Pico
17 parts399MIT
KiCad boards from 4 GitHub repositories tagged “ps2-keyboard”, the most starred first; open any of them in PCBKit.

No0ne/ps2x2pico
USB keyboard/mouse to PS/2 interface converter using a Raspberry Pi Pico

ChrisDeadman/usb-to-ps2-gameport-hat
Convert USB devices to PS/2 & Gameport devices with the power of Arduino 🙂

sam-was-here/PUMBA-Keyboard
PUMBA-Keyboard is a PS2 to USB macro board adapter

flyboy-byte/riscv-pico
Real Linux on a Raspberry Pi Pico, with its own PS/2 keyboard and VGA screen — the RP2040 emulates a RISC-V CPU, SPI PSRAM becomes system memory, and the guest drives real GPIO pins.