You can order potentiometers from digikey or mouser. Most times there is a code on the part that will tell you the required resistance, got any up-close photos? Look for something like 3 numbers - 203, 104, etc.
Then it’s a matter of finding one that’s close, and fits. Grab some calipers and measure the distance between the pins.
Of course just because the volume doesn’t work, doesn’t mean it’s the potentiometer that’s faulty. Do you know it’s that part for sure?