Screw size question

Does anyone know the screw size for the end cap on these AF guns? I finally found a supplier stateside that sells an LDC adapter end cap for them, but the factory screw is now too short. It’s on there fine for now, but before my new LDC gets here, I’d like to get a longer screw to fully engage the threads. I don’t want to take the little screw with me to the hardware store, for fear of dropping and losing it. I tried to search the web, but I’m not getting any hits. I also tried looking at the Quick Review on here, also no joy. TIA!