Best Buy via eBay offers the Tile Mate Bluetooth Tracker 4-Pack [ebay.com]
for $49.99 with free shipping. (Amazon [amazon.com]
and Tile direct [thetileapp.com]
charge the same.) That's $12.50 each. It attaches to something that you don't want to lose, such as keys or a backpack, and can be tracked from Tile's iOS and Android apps.
Need it for Christmas? For expected delivery via Best Buy, order by December 20 at 11:30 am ET. For Amazon, order via Prime by December 22. For Tile direct, select free "Priority" shipping at checkout and order by December 20 at 7 pm ET.