Original - Gaggia Classic PID kit - 1/32DIN single display
PID Retrofit KIT for Gaggia Classic Pro & Classic & Home PID Temperature Control Retrofit KIT for Rancilio Silvia Espresso Machine [KIT-GG] - $149.50 : Auber Instruments, Inc., Temperature control solutions for
PID Retrofit KIT for Gaggia Pure & Color [KIT-GP] - $144.95 : Auber Instruments, Inc., Temperature control solutions for home and industry
PID on Gaggia Classic Pro - Game changer to budget espresso brewing at home - YouTube
Restoring a Baby Gaggia machine (full album in the comments!) : r/gaggiaclassic