My shower diverter allows about a third of the water to flow to the tub faucet. I took it apart and think I need one of "these". If you can see the photo, the interface is eroded or damaged. Where can I get this, and how do I specify part number? I think it is a delta, but not sure.
If that is a push button diverter on a Delta valve body, then you need a complete new diverter, and the push button should have hit you in a sensitive part of your body when it flew out of the valve.