If you'd like to purchase an I/O Expander kit for your PiDP-11, assembled boards are available for purchase from Tindie: https://www.tindie.com/products/sstallion/pidp-11-io-expander-kit/

This kit contains everything needed to expand the I/O capabilities of your PiDP-11:

• I/O Expander PCB (Assembled & Tested)
• Jumper Wires
• Pin Headers
• Double-Sided Tape