Apple launches battery replacement program for 13" MacBook Pro without Touch Bar
MacBook Pro 13" Unibody Early 2011 Battery Replacement - iFixit Repair Guide
Amazon.com: SLE-TECH A1321 Battery for Apple MacBook Pro 15" inch A1286 (Only for Mid 2009, Early/Late 2010), fits MC118LL/A MC373LL/A MB986LL/A Series Notebook : Electronics