Guess who managed to score an original PowerBook G4 titanium battery in mint working condition with only 41 cycles on for just £10. An accidental miracle. Facebook market place to the rescue! :
Apple Powerbook Battery - G4 Titanium 400/500 PRAM - 922-4361
820-1484-A Apple Pram Backup Battery for PowerBook G4 15-Inch A1046 (Refurbished)