They have them listed on the Karmic website, but the website seems broken so I'm not sure if they're still in business. Try contacting hong@karmicbikes.com
The HP0180WL4 charger seems like it's used for a range of devices based on this site, but they only sell 200 of them.
The only other option I can think of is to get a charger which is matched to the voltage of you battery. I believe the Karmic Koben S has a 44V battery from what I read about it, but please confirm this before choosing a charger.
Cooling: Built-in fan. -Input plug: US/EU/UK/AU for choice. -Compatible Battery: 24V/36V/44V/48V/60V for choice. -Multiple choices for your need. -Output interface: 5 types for choice.
www.ebay.com
Please note, always charge your battery outside of your house and well away from anything flammable and don't leave it siting on charge over night.
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