If not you can use some pet tracking device, like FindMyCat. It’s a small opensource device in a collar where you need to plug in a SIM card.
But if you want a device which uses low power Bluetooth / mesh connection and which doesn’t require SIM card nor GPS. Then I don’t know any alternative which is not a privacy nightmare.
If you can hide an old small android phone with a a SIM card in your bike, you can use FindMyDevice (FMD) available in f-droid.
If not you can use some pet tracking device, like FindMyCat. It’s a small opensource device in a collar where you need to plug in a SIM card.
But if you want a device which uses low power Bluetooth / mesh connection and which doesn’t require SIM card nor GPS. Then I don’t know any alternative which is not a privacy nightmare.