MacBook Pro 15" Retina (Mid 2018-2019) Battery - iFixit Store
Hyper Juice: 99Wh Battery Pack with 100W Charging for ~$400
A1322 Original Battery for A1278 Apple MacBook Pro 13 inch 2009 2012, A1322 Battery for Apple MacBook Pro 13 inch A1278 (Mid 2009 – Mid 2012) - WIT Computers
Amazon.com : ChugPlug Portable External Battery Pack for Macbook Air and Pro (45W and 60W) : Electronics
11 Portable Batteries for Your MacBook — Best of - Hongkiat