T-Mobile recently came out with some little trackers that have a cheap monthly fee. They work off cell service not GPS, but as long as you aren’t way out in the sticks I bet it’ll work fine.
https://www.t-mobile.com/iot-devices/syncup-gps-tracker-device
I’m going to get one for the next RV we get. AirTags are cool, but they will notify they thief potentially and I don’t want them knowing that they should be digging for a tracker.