This inexpensive 9 volt power supply has a 2.1mm plug which powers common effects pedals and electronic devices. It has a small footprint and can run in any power outlet worldwide.

This power supply is not compatible with Boss or the KOMA Elektronik Kommander. You want the Negative Tip version here.

Polarity: Positive Tip
Output Voltage: 9VDC
Output Current: 800mA