Are you sure it is 45057, or is that just what the seller said? Some sellers are not aware of the two types made:
The pistol grip for the motor bodies looks superficially the same but the release trigger has a different shape, there is no code number on the part. It is 46221 and is much less common and commands a higher price. They are not compatible with the "wrong" body.
Try to Google both numbers and compare images with which you have, I suspect you have the motor body version.