This is for tents, but it may help https://lightheartgear.com/blogs/news/repairing-damaged-window-netting-in-your-tent
Net sunshades, to me, means that it is woven like a fishers net.
If this is the case you’re going to have to think in terms of finding matching rope or twine or whatever it is.
Then you need to look into things like tying macramé knots or things like crocheting techniques.
Maybe get a piece of matier that matches n hand sew it like a patch !!??
Net (first picture) or mesh (second picture)?
What material is the sunshade made out of? Nylon? Rope? Plastic?
Posting a picture would be helpful in illustrating what the actual fabric is.