How is this EEPROM fully addressable?
It's a 64k bits device, i.e. 8k bytes, which needs 13 address lines: \$2^{13}\$ = 8192 = 8k bytes. The Winbond device is indeed 64k bytes.  

Looking at available devices at Mouser I noticed that 64K devices are not that common, and not at all in DIL package. It may be better to use two 32K devices, they seems more common, but still expensive. Maybe your best option is to use Flash. You can find Flash devices at a fraction of the price of an EEPROM, yet having twice the memory capacity. (warning: the example is 5V only.)