A more common name for this type of fan is Squirrel Cage Fan. Here are some 12 volt models, but would probably give you decent flow at 8 volts:
EDIT: Actually running a 12 volt fan at 8 volts is a bad idea, since power will go down linearly with voltage and fan flow will go down by cube of power ratio. The flow at 8 volts will be 30% of what it would be at 12 volts.