Ah, I see what you mean now.
I have only seen side camera covers for Teslas, not Nissans. And based on their design, I think those covers are only for physical protection, not for rain/dust protection.
For a DIY camera protection against water, you can try using the stick-on type side mirror waterproof films. They look like a big phone screen protector. You will need to cut them to shape, fit and stick on your camera lens. I have only seen them sold online. However, they are meant to go on a flat (mirror) surface, so I am not sure if they will hold well on the curved camera lens.
2018 Nissan Leaf S w/QC
Placed in action: 9/2018