Tried opening up your current one? Very easy usually and lion batteries just connect with a JBOD connection. Google the battery size and get new one from Aliexpress. It’s not rocket science!
Then you’ll love your current mouse even more knowing you saved it from trash :)
I’m currently replacing the right click button in my MX master 3S. 5 euro for 10 switches and a bit of solder. Not for everyone but batteries are much easier :)
Got an aliexoress one, carbon one side, texture the other. PETG doesn’t work on the carbon side, but for textured side I love it.