12V to 5V USB Power Converter

I replaced my existing motion detectors with Indoor Google Nest Cams. These cams have a male usb end so I ordered this power converter with female usb end. I doubled up the wires, black + green and red+ yellow on both ends and connected to a terminal adapter to 12v power adapter and voila, hardwired power to my cams without running wires along the wall to nearby outlets.

After several years of building a sizable home-automation situation, I decided that I'd move from our legacy (and expensive) security system to a wireless security system. I bought a 10-piece kit at a big membership warehouse store and let it sit for a while. When my father was about to move into an apartment, I offered the dusty kit to my brother to install for our father. He did the install and when we talked about it, he said it went so well that he intends to buy a couple kits for his new retail store.

Anyway, this review is not to extol the virtues of that wireless security system; it's about what I used this converter for.

When visiting said apartment recently, I noticed that the system's front-door keypad had a cable dangling from the keypad, terminating in a 120v-to-USB adapter which was plugged into a wall outlet. I thought the cable looked ugly and when contemplating buying another wireless security system kit for myself, wondered if there was a way to eliminate -- or easily conceal -- that ugly cable.

In fact, I think I said out-loud, "Since I plan to replace our legacy system's keypad with the wireless system's keypad, I wonder if they make some sort of adapter so that I can use the power going to that keypad and convert it to 5-volt USB..."

Well, a little something-searching around (maybe with some help from Reddit?) and I learned that, indeed, there are indeed such converters and that the keypad power is typically 12-volt, so it was just a matter of…