U.S. "half and half" is a mixture of whole milk and cream, making a very light cream that is great for coffee. It's widely used and available in every grocery. It would be possible to make it in Bs As by combining leche entera and crema, but not very convenient.

As for coffee, I've found "100% Colombian arabica" at the supermercado, and for a while the Disco carried a Melitta Brazilian 100% arabica that was actually pretty good and not expensive.