Many legacy iOS communities maintain archives of old IPA files. You will need a computer with (now mostly defunct) or AltStore (requires iOS 12+ for the server component) or Sideloadly . Sideloadly works on Windows/Mac and can push an IPA to iOS 9.3.5.
Look for "Netflix iOS 9.3.5 IPA" on reputable archive sites like or Archive.org . netflix ipa for ios 9.3.5