Look for "Retail" or "DVD" tags on subtitle sites. These are ripped directly from official releases and are almost always perfectly timed compared to "Fan-subbed" versions.
: Usually the most comprehensive database for older TV shows. Kung Fu (1972) subtitles
: Ensure the subtitle matches your video source (23.976 fps is standard for North American DVD rips). Look for "Retail" or "DVD" tags on subtitle sites