Now make it recharge when you rewind the tape.
or just steal power from the constantly rotating tape mechanism. That would be really cool.
I use a wired cassette adapter in my cars, because I just hate having battery driven devices that connect to battery driven devices etc etc, and it’s just managing power all the way down.
People will do literally anything except swap out their old stereo for a modern aftermarket one. I’ll never understand why, especially given how easy it is to do in older cars. Much easier than turning a cassette tape into a Bluetooth receiver, that’s for sure, and you’ll get modern features like backup camera support and Android Auto too.
If I could buy one of these things I wouldn’t have to put a new stereo in my old '95 work truck to use bluetooth (assuming the tape deck still even works). I just use an earbud right now.