Finding those kinds of stories is a real deep dive, honestly. You're not going to have much luck on the big, general fanfiction hubs—the pairing is a pretty niche take on the whole gender-bend thing. I've seen the most activity on dedicated Naruto forum archives that are a bit older. Places like 'Fanfiction.net' have a few, but you've got to be real specific with your search tags, and even then, the quality varies wildly.
Honestly, my best finds have been through following authors. If someone writes a solid 'Naruto' character study or another interesting AU, sometimes they'll dabble in a 'Naruko' variant. I remember one writer on 'Archive of Our Own' who did a whole series reimagining key arcs with that dynamic; it was less about romance and more about exploring identity, which I found way more compelling than the usual stuff. You kind of have to be willing to sift through a lot of weird power-fantasy self-inserts to find the good ones.
It's a pairing that tends to attract either super introspective work or, well, the opposite. Discord servers for older anime fandoms sometimes have dedicated channels for sharing links to those more obscure story repositories. Don't expect a huge, trending tag anywhere, though.