This is a Little Modellfinder like an Hellgate Buzzer https://buzzer.hellgatefpv.com/
the black one is my smallest version with 70mAh Lipo
Parts you need:
-2x 10K Resistor
-little 1s lipo from scratch 50mAh to 200mAh
-Attiny85
-5V active Buzzer
-5V PowerSupply from FC or Reciver
-TP4056 Lipo Charger module like this with undervoltage Protection. https://www.ebay.de/itm/5-5V-1A-Micro-USB-18650-Battery-Charging-Lademodul-Schutzschaltung-TP4056/123286323604?epid=14019161893&hash=item1cb4700194:g:0EwAAOSwyCNbYZML
One tricky thing is to modify the Charger that it doesn´t charge with 1A current.
for this please look inside the Datasheet.
You have to Replace the Resistor, next to gnd input, with a 10k Resistor for 140mAh charging current. That is completly enough.
Connection Diagramm
