Looking up door hardware terminology, that specific piece may be a "keeper."
This is the closest thing I found, but it's both discontinued and too large based on your pic.
Google image searches return things somewhat similar to your part, but not exactly the same. In terms of online research, your last resort may be to unscrew it and take pictures of it from different angles, upload them and do a reverse image search.
Or, just broomstick the track.