u/Apples_to_Apples_16

Prius 2010 w/185mi (1.8L L4 - FULL HYBRID EV-GAS)

Ok so, just had to replace my battery because it was literally submerged in water and corroded. The suspect I have for where the water is coming from is the rear bumper cover grommet. I've found the part online (Part No.: 52599) but I can only find the screw and not the part that it screws into. Could anyone help me find it? I also am wondering if I should do anything else to my Prius to help with water leakage while I am at it. I saw another post where people recommended re-doing the seals on the car but I am not sure how I would go about that. I am a new car owner, any help would be appreciated!