If you have a standard bathroom sink or bathtub without a complex lever mechanism, the solution is buying a universal replacement.
Most household drains are standard sizes, but you should measure to be sure. diy drain stopper
One‑time use when you need to fill a sink immediately. If you have a standard bathroom sink or
A sturdy plastic bag (like a freezer or Ziploc bag) and water. How to do it: Fill the bag about 3/4 full with water. diy drain stopper
Here’s a helpful article you can use or adapt.