Okay, so you're hunting for that very specific flavor of hurt/comfort, I totally get it. That premise is like catnip for a certain mood. Honestly, your absolute best starting point is Archive of Our Own—AO3's tagging system is a lifesaver. You can search for 'Uzumaki Naruto', filter by the 'Rejection' or 'Family Rejection' tag, and then sort by kudos or bookmarks. You'll find tons. Wattpad has a huge volume too, but the quality can be really hit or miss; it takes more digging. Sometimes I just search the phrase 'rejected by family' on there and scroll.
A lesser-known trick is to check fanfiction.net for authors who cross-post. The site is older, so some real classics are buried there, but the search is terrible. I often find gems by looking at the favorites lists of authors I already like on AO3. Also, don't sleep on Tumblr. People often post snippets or links to their full works on there, using tags like #naruto fanfiction or #hurt naruto. The community curation can lead you to some amazing, under-the-radar stories that haven't blown up on the big archives yet.