Sustain pedal, deluxe model metal, switchable polarity
This Boston sustain pedal can be used with all digital pianos, midi keyboards and controllers, due to its polarity switch and is modeled after damper pedals as seen on acoustic (grand) pianos.

You can connect it to your device with a 1/4" jack connector.

If you own a keyboard with adjustable control pedal settings, you can also use the BFS-40 as a footswitch.