I like the idea of pocket-sized hobby electronics. This seems like a simple project to make and design yourself though I'd never personally use this (in particular: I have a handbag in practice when I'm in the city, so its more likely that a cutpurse would cut my strap and steal the whole bag rather than reach into my pocket).

From this perspective, the T460 Motorola Talkabout walkie-talkie is the pocket-sized electronic device that inspires me. 3x AA batteries coincides with 3.6V NiMHs (though nominal can be as high as 4.5V if you use Alkalines instead), and 3.6V coincides with 3.7V or 3.6V Li-ion that's grown more common today.

T460 is an antenna, LCD Screen, a few buttons, a board, and the 3xAA all in one (larger) pocket-sized device. So that's why its my inspiration. And I also think that AAs / NiMHs are easier to use than Li-ion for hobbyists (though Li-ion obviously shrink down more easily by being single-cell). 3x AAA or 3x AAAA could shrink down the size to this screamer, and I'm sure that there are parts that handle 2x AAAA (aka: 2V to 3V Alkalines) with a reasonable amount of noise and battery life if you really needed to shrink down.

1x AA is doable with a boost-converter, and I've found many flashlights designed around 1xAA + boost converter in practice.

Anyway, just musing upon different formats. I guess 1x AAAA with a screamer based off of the MCP1640 Reference Design (https://www.microchip.com/en-us/development-tool/mcp1640rd-4abc) is what I'd go for a pocket-sized solution to this simple problem, if I were to design something (or maybe size it up slightly to 1x AAA or 1x AA size, since cheap rechargable NiMH cells are available at the AAA and AA sizes).

I'm not sure if the whole design would fit inside of the "matchstick", but it shouldn't need to be too much larger than this in practice. Replace the "button" with the light-sensor and the reference design is pretty much where you'd want a device like this.