just buy an external USB or firewireHDD, and use that.
there are such devises well above 500Gb
here you have one such (40Gb), it is powered by the USB port and is aboutthe size of a pocketbook.

http://www.dustin.se/dacsaportal/sys...dID=5010093553

yes i know it is in Swedish, it was what i could dig up in a hurry. it is more to show you what i mean.