I just searched and found out that a company called C-guys actually made an SDIO card for the Zaurus including Linux drivers, the GP2X has got quite much sales, maybe they would be interested in making a card for it as well? They made both 801b and g cards.
http://www.c-guys.net/
http://www.c-guyseurope.com/
http://www.c-guys.net/
http://www.c-guyseurope.com/