According to this story at TheiBook.com the 12-inch iBooks have been End-Of-Lifed (EOL):
After talking with CompUSA and one independent retailer, it appears that the iBook G3 500 12? and the 600 12″ status was changed to EOL on January 7, and today they are just beginning to run out of stock. Model numbers from the replacing (Rev C) iBooks are already in the distribution system, and records show that the new iBook revision is already available in the distribution channel.
