Spare screws

One of my doorbells needs recharging frequently because it struggles with Wi-Fi. I suspect it’s constantly working hard to locate a signal. Not much I can do as big old house with thick walls and power line adapters plus chimes already located in every spare socket. The need to constantly remove and reinsert the tiny screws just to charge up the battery is intensely annoying. I lost one this morning. Why is it not possible to purchase a pack of, say, a dozen spare screws instead of a whole installation kit with a load of stuff one doesn’t need? I’m also afraid of wearing out the screw heads.