Tracker battery replacement
The batteries inside a tracker can be replaced. Bad news: It's a weird 3.85v battery, and there's no space inside the tracker to actually use a larger one so you're still basically stuck with a fresh replacement rather than upgrade.
good news: these batteries are available and aren't expensive.
Model: B2PYV100
What to look out for: chinky batteries aren't worth the $10 you save, they are often worse than the worn-out battery you're replacing. Get batteries from a reliable retailer; they should have blue/green/black cables, not red/white/black.