Synergy Digital Laptop Battery, Compatible with HP Probook 4720s Laptop, (Li-ion, 14.4V, 4400mAh) Ultra High Capacity, Replacement for HP HSTNN-1B1D Battery - Walmart.com
HP ProBook 4720s Laptop Battery - 6 Cell 5200 mAh - YouTube
Laptop Battery for HP ProBook 4510s 4720s 4510s/CT 4515s 4515s/CT 4710s 4710s/CT | eBay
HP ProBook 4720s Laptop Battery - 9 Cell 7800 mAh - YouTube