UltraLast 3.7V 1050mAh Li-ion replacement battery for Logitech devices - HHD10255 at Batteries Plus
Logitech Harmony Ultimate Battery for Remote Control
Logitech Harmony Is Dead. Here's How the Smart Remote Lost Its Way | WIRED
Amazon.com: Synergy Digital Remote Control Battery,Compatible with Logitech Harmony Touch Remote Control, (li-ion, 3.7V, 1100 mAh) Ultra High Capacity Battery : Health & Household