Amazon.com: GHU Premium 58Wh Battery PR06 Compatible with Battery for HP ProBook 4530s, 4540s, 4430s, HP Spare 633805-001, QK646AA - UL CE FCC Tested, Long-Lasting, Easy Installation, Reusable 500 Times : Electronics
Genuine PR06 633805-001 Battery for HP Probook 4530s 4330s 4430s 4440S 4540S – Tacos Y Mas
633733-421 - PR06 6-Cell Battery for HP ProBook 4530s 4535s 4540s 4436s 4430s 4330s 4435s - CPU Medics
HP ProBook 4540S battery,4400mAh battery for HP ProBook 4540S laptop(6 cells,10.8V)
Amazon.com: New K104 Notebook Battery for HP Pavilion 14-ab 14T-ab 15-ab 15-an 17-g Series TPN-Q158 HSTNN-LB6S Spare 800049-001 800050-001 800010-421 800009-421 KI04 Notebook Laptop Battery - 12 Month Warranty : Electronics
HP ProBook 4540s Battery Replacement - iFixit Repair Guide