I found this Morley Volume pedal at a garage sale for $5. I think it was a good deal. Not as sturdy as the Earnie Ball, it still feels pretty solid.
It has a big toggle switch at the toe which turns it off and on. Not sure why you’d want to turn it off except to conserve the battery.
And yes, it does require a battery. Instead of pot the Morley uses an LED/LDR to control the volume. The pedal attaches to a piece black card stock that passes between the LED/LDR pair as you move the pedal. Simple and effective.
It takes a 9V battery, or power supply. The power supply requires an 1/8″ mono jack, which is less than idea, but I have an adapter so it’s a non issue. Placing the Instrument, and Amplifier jacks on the same side (right) is a little problematic. Then again it might work out better for some arrangements than others.