I don’t often have leftover wine but when I do I use Vinum Meum Glass Stoppers. They come in two sizes that fit most bottles and are easy to use. Two nice features are that you can lay down the bottle and that the stopper does not add height so you can also use in fridge door.
The card enclosed in my order says that “When you shop with Vinum Meum you are not helping a CEO purchase a yacht and a brand new car”. I love to help a small company get out there when they have a good product.