You could also just open it up and check if the wires are broken maybe and resolder them, or replace the piezo, it needed.. (e.g https://www.amazon.com/Goedrum-Pack-Prewired-35mm-Piezo/dp/B00UC4S6A0)
They kind of look like DIY percussive elements. The white pad sounds like a snare. Commercially, there is the SamJam. I've never used one, but have totally thought about getting one before.
The circle he's hitting with his thumb, I'm not sure, but it sure it pronounced. It makes me wonder if he's got a piezo disc in there running to a separate input or amp to get that sharp sound. I've not seen one mounted to a guitar, but as a sort of pedal you can tap with your foot they're totally a thing.