Is there a Hack for Charging from USB instead of Firewire?

Is there a Hack for Charging from USB instead of Firewire?
Is there a way that the charging components inside a 3rd-gen iPod can be changed from Firewire to USB ?

answers:

This incredibly compact DC step-up converter is what I used. It fits neatly inside the 3G case behind the hard drive.
Hi Friends,
One option its just an adapter with firewire for the car.