Edit: As pointed out below, this is apparently a generic answer by kobo. Apparently the Glo uses 5v 800 mAh.
http://kobo.intelliresponse.com/answ...y+Kobo+eReader
5v 500 mAh is what Kobo says to use, and I would not go too much higher mAh's or you risk messing up the charging circuit.
Computer USB ports output at 5v 500 mAh, but most USB chargers sold with electronics today output higher volts and amps. I know people say other chargers work, and some have even said as long as the plug fits it will work, but while other chargers may work, you should use the correct voltage and amps for the unit. The statement "if the plug fits it will work" is not only ignorant, its dangerous.
Lithium ion batteries incorrectly charged EXPLODE. I saw the end results of a someone who put LI batteries in backwards to a high end flashlight that did not have a reverse circuit protection and the batteries exploded. Not a huge explosion, but enough to vent a corrosive gas out of the split battery which ended in a broken expensive flashlight.
Do not take chances. Just use the correct charger.