look on the pump itself, it should have a tag on it with the mfg make and model and serial of the pump. try searching for it using that information.
chances are they just updated the pump to a newer model, it is unusual for mfg's to stop production of a part without having a updated replacement unless they discontinued the production of the whole lift. In most cases they usually use that pump in multiple models as well. Unless like i said, they updated to a newer model pump.