Looks like the firmware is indeed a 138,752-byte file in the firmware updater program:
SeriTek1S2Flasher.app/Contents/Resources/ROMFILE.1S2
I'd try to help patch the flasher, but my PowerPC assembly skills are very, very limited. I wonder if it's possible to use a PC-based flasher to flash that file to the card? What does the ROM chip look like on the board? Is it socketed, or (more likely) a chip soldered to the board?
SeriTek1S2Flasher.app/Contents/Resources/ROMFILE.1S2
I'd try to help patch the flasher, but my PowerPC assembly skills are very, very limited. I wonder if it's possible to use a PC-based flasher to flash that file to the card? What does the ROM chip look like on the board? Is it socketed, or (more likely) a chip soldered to the board?