The problem is conceptual.
There are two types of tracker devices.
AirTags, and similar devices in the Google ecosystem, are short-range Bluetooth beacons. They don't actually have GPS receivers of their own. They rely on the swarm of other Apple / Android phones in the world that have their Bluetooth radios active. One of those phones picks up the beacon, and sends a report up to Apple / Google with its current location and the beacon signal strength. That is how you can find your stuff, because some random person's phone called in a sighting. Because these things are very simple, just a very low power Bluetooth transmitter and nothing else, they can run for a year on a coin cell battery.
The other is an actual GPS tracker. This device has a GPS receiver to determine its own location, and a cellular radio to transmit that location elsewhere, often just by sending a text message with its ID and location to some server. This however is physically larger because you need a battery, GPS antenna, cellular antenna, and a cell phone style radio chip. That all uses a lot more power. Most of the ones designed to last for months have a power brick holding 4-8 D-cell batteries, or a large lithium pack. Obviously that is not some tiny thing you lose in a pocket. Those are usually magnetically attached to the bottom of cars. Or, in the case of fleet telemetry, it will be hardwired into the vehicle. But this sort of thing necessarily requires a subscription fee because it has a cellular radio. That cellular thing needs an account with a carrier.