Gigabyte tend to have support downloads for everything they have made, dating back a long long way. The board you are trying to get is not listed, which suggests that it was an OEM only board. Does that sound right?
Unfortunately I dont know as was not with the company then, all I know is that the company who supplied the systems went bust, hence why we are in this predicament!! All I would say is that it seems odd that we have managed to pick some up on Ebay from various sources which led me to believe thet were original boards in general use, but may be mistaken.