So here it is, the firmware everybody's been searching for:
http://www.savefile.com/files/1414352
It's a 9.1.52 firmware for MP4 players with the G-18A-Main-V0.3 Board, TGS177SH00 screen and the AK1025 chip. I don't know if it goes for all of them, but my player is a 3rd gen Ipod nano clone with a real ipod connector.
I couldn't upload it here so I uploaded it by a file hosting service.
Good luck!
/Knasen