Tiny and cheap Wireless HID device

Hello fellow hackers, I am new to this forum but thought it might be the best place to start.

I opened up a 5 dollar Bluetooth HID mini keyboard. does anybody have knowledge about the build, the chips (which are blanked), and if there is anything other available than an ESP32 or similar that can emulate HID over Bluetooth. This is such a cheap device that comes with an (I guess 2.4) dongle, a lithium chargeable battery, a USB cable. It is a fully functional wireless keyboard with a tiny footprint for under 5 dollars. I would be happy to see is I can build a wireless HID so small myself.

Any info would be appreciated. Thanks :)

Images: https://ibb.co/nR6PvsD https://ibb.co/FYqBsw7 https://ibb.co/LzJX2hV