The LED that’s in those bullets is a 0.5 Watt 5mm LED similar to this:
I bought a copper bullet branded Astrolux (i think TB-01 ?) with pretty powerful 3x LR41 inside plus 3x LR41 spare batteries a few years ago from Banggood.
I estimate it’s around 15 Lumen with fresh batteries, maybe even 20 Lumen.
Pretty impressive for the size.
Those Mateminco branded ones are crazy expensive.
Here’s a stainless steel one:
https://www.aliexpress.com/item/32844630381.html
You can see the brand name is photoshopped away, but i bet it says Astrolux.
Here’s an aluminium one:
https://www.aliexpress.com/item/32839012681.html
Either way, yes it would be nice in high CRI warm white, but Djozz tried it with a Yuji 5mm LED iirc, and it was much much less bright.
These LEDs here will do a better job, but still a lot less than the stock LED.
I think these LEDs are better suited for lights like this:
https://www.aliexpress.com/item/32885217288.html
https://www.aliexpress.com/item/33023962121.html
https://www.aliexpress.com/item/32923872041.html
https://www.aliexpress.com/item/4000385078691.html
https://www.aliexpress.com/item/32775843914.html