The pedal was designed so any linear 10K potentiometer will make the pedal to function. (or you can even try 100K and it should work the same)
The problem is that the holes are made for the RV16 series, so it is not easy to find an alternative.
If you are good soldering and working with your hands, you can try to use any 10K linear pot that you know and wire it to the holes on the PCB.
If I find any Mouser alternatives I will let you know anyway.