I also have Vitz 2003 model and my fuel pump was dead, my mechanic replaced it with Orignal GLI Fuel Pump, dono hight main thora sa difference tha liken width dono ki braber thee. It has been around 3 years it is working absolutely fine.
Old/used pumps kisi kaam ky nhe hoty bar bar kholny aur band kerny sy gari ki baj jati hy, always install brand new and genuine parts in your car.
If you live in islambad I can give you the number of mechanic.