Looking at this charger, trying to figure out the measurements so I can get the correct plug
A correct plug for what? What’s your application? does it need to be water resistant? is it a thin or thick casing? Come on man contain all of your questions and goals in one place. You have already received a warning from a mod. Not only that but you will get better answers to your questions in the right context.
Output plug : 5.5 * 2.1 * 10mm DC Power Male Plug Jack Adapter Connector Socket