Coca-Cola is the only company that can legally import and process raw coca leaves into a flavoring agent. It’s literally impossible to duplicate their exact recipe.
If you live in the US sure. I live in a Latin American country where it’s legal to buy coca leaves (cocaine is illegal obviously, but the leaves aren’t and are commonly sold in health food stores of all places for tea).
Stepan Company, actually. But you’re right that Coca-Cola is the exclusive buyer.