Stronghold Missing End Portal

After defeating the wither, my friends and I decided to finally search for a stronghold and defeat the ender dragon. After hours of searching for a stronghold, we found one. We then searched the stronghold itself, which had no end portal whatsoever. It had a large library, and a couple hallways, nothing else. What can I do other than traveling another 5,000 blocks to find another stronghold that may or may not have a portal?