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See this article for some information about high power USB ports on a Mac:
Apple Computers and Displays: Powering peripherals through USB
My suggestion would be to see if you can find a powered USB hub that is capable of delivering that amount of power.
I am skeptical of you finding it because I believe the 5V and 500 mA is in the USB spec.
No matter what the Mac can't do it.
The only other alternative I can think of is to talk to the vendor of the device to see if they can supply with something that provides that amount of power.