Amazon.com: Replacement Individual AP11 Type Left Option(alt) Key Cap and Hinge for MacBook Pro Model A1425 A1502 A1398 for MacBook Air Model A1369/A1466 Keyboard to Replace The Left Option(alt) KeyCap : Electronics
Where is the Alt key on Mac? Here's how to find it.
MacBook Keyboard Guide, Symbols & Special Characters | Keyshorts Blog