Ask HN: Alternative for Apple AirTag for ebike battery theft detection?

Someone stole my wife's bike battery while it was parked in a bike stand in Amsterdam :-( She was so pissed because she had secured the bike itself very well, only to realise the thief easily broke the lock for the battery and stole it leaving us a EUR 1000 damage.

Since then, she has been paranoid of her bike getting stolen and would like a GPS tracker on it. First thing came Tony mind was Airtags, but it is essentially useless in this scenario because it would prompt the their if they had an iPhone saying "you have a AirTag following you".

Is there an alternative to use for this need?

P.S - I already read about 1. Trackers based on a 2G SIM network - I don't want to use it because finding a 2G SIM is a pain, and it would just go unsupported very soon.

2. There are ones that need a pricey subscription to the tune of 4 Euros/month. I think it is too expensive. The maximum I'd spend n this is 2 EUR a month.

3. Tile would not be so useful because they rely on other Tile users which may not be close enough to be useful.

Any ideas?