The volume pot I used was part number 168-386, I bought it from RS Components in the UK.
TE Connectivity 27 100 kΩ Rotary Potentiometer 1-Turns 2-Gang Panel Mount, 27ESA104MMF50N | RS
TE Connectivity 27 100 kΩ Rotary Potentiometer 1-Turns 2-Gang Panel Mount, 27ESA104MMF50N | RS