The Toshiba extraction tool can be downloaded here here. It's used like this:
toshiba_remap.exe -in bank1.img -in bank2.img -out output.img -bmsize (number)
bmsize (number): The output file size in 16K blocks.
NOTE: W54t requires adding ``-w54t`` as an argument
toshiba_remap.exe -in bank1.img -in bank2.img -out output.img -bmsize (number) -w54t