If you have a standard bathroom sink or bathtub without a complex lever mechanism, the solution is buying a universal replacement.
Before you build a new one, your current stopper might just need a simple fix. Many "broken" stoppers are actually just disconnected or out of alignment.
Hardware stores sell "Universal Drain Stoppers" for under $10. They usually come with a rubber plug and a metal basket that sits inside the drain.
As you fill the tub or sink, the downward pressure of the water will suck the lid onto the drain, creating a firm seal. 4. Creative Household Alternatives
Push the bag firmly into the drain hole. The washcloth provides the structure, while the plastic provides the waterproof barrier. 3. The Jar Lid Suction Method
Fill a heavy-duty storage bag about 3/4 full with water and seal it tightly. Lay it over the drain; the weight of the water creates a leakproof seal. For extra security, some DIY enthusiasts suggest using double bags.