I'm thinking of going with a SPOT Trace tracker, you can find some info here:
https://www.findmespot.ca/en/index.php?cid=128
Weight: 87.9 g (3.1 oz)
Height: 6.83 cm (2.69 in)
Width: 5.13 cm (2.02 in)
Thickness: 2.14 cm (.95 in)
It uses 4-AAA batteries and they are good for almost a year in the device.
and I love that it rely on Satellite to send it's position data to there server, you can then receive either a text or go directly on a map using there mobile app and track it's position. With the basic subscription you can set the update time at 5 mins so it's not that bad....