Did you end up finding a charger?
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 firstname.lastname@example.org
The HP0180WL4 charger seems like it's used for a range of devices based on this site, but they only sell 200 of them.
HP0180WL4 48V3A ELITE China, Model No.: HP0180WL4（13S）48 V-3 A Li-ion Battery Charger Specifications: Input Voltage:100V-240VAC ( 50/60Hz ) Output Current: 3.0A±0.1A Output Voltage: 54.6V±0.2V
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.
Find many great new & used options and get the best deals for 24V/36V/44V/48V/60V Li-ion Lithium Battery Charger For Electric Bicycle E-bike at the best online prices at eBay! Free shipping for many products!
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.