I've had good experience charging my Kobo with a Motorola Razor charger which has a mini usb. This also gets around plugging into my computer. I left
the charger in the country on the week-end and my phone was dead so no charger other than the one in the car. I went over Yonge St in Toronto and bought an off-brand charger for Motorola cell phones for $7.99 CDN. Works great on both the phone and Kobo.
I wonder sometimes whether or not the direct charger is more effective/efficient than through the computer. I always leave it charging until the red light goes
off and then still leave it on until I get around to removing it.