Might need a left and right gasket for the rear tail lights. I potentially have a water leak there. So if I'm going to the trouble of taking the tail lights out, I might as well replace the gasket. The last I heard, it wasn't available. As a last resort, I could call a dealer to find out. But this is more fun. Thanks.
If you are having trouble finding the gaskets, you can go to your local hardware store and get High Temperature Silicone which works well as a replacement over the gaskets.
There are many threads on here about water leaks in the trunk area. That is typically not where the water comes in. Water leak...into spare tire area etc | PriusChat Water leaking into battery well through seam above right rear passenger tire - anyone had this ? | PriusChat Have you ever had any body work done on the rear of the car?