The only thing i know is that you've to use some kind of backup unit. Look here, maybe this is what you're looking for:
http://www.lik-sang.com/catalog/prod...p?category=43&
What i found on the net:
"dumping" (backup units)
ROMs are made from game cartridges with hardware devices known usually as backup units. These are available for purchase over the web. The cheaper devices must be connected to a PC (via a cable to the parallel port) in order to upload or download ROMs, the more expensive ones contain writeable media drives such as the Zip, or conventional CD-ROM drives, so they can be used independently of a PC.