There are many scallion substitutes available at your local grocer that can complement a wide variety of your dishes in a similar way.
Scallions are often known as spring onions or green onions. They are young onions that are harvested before the round white bulb has the chance to mature. The long, green, hollow leaves are chopped, eaten raw or cooked in salads, soups, and used as a garnish. Scallions are especially popular because of their mild taste and crunch. 
Most grocery stores will have scallions in their produce section, but scallion substitutes are likely nearby. If you can’t find scallions, there are several other vegetables you can substitute in their place such as chives, ramps, shallots, and garlic scapes among others. Let us take a closer look at them below.
Chives are part of the same family as scallions, onions, and leeks. They have a similar flavor, look, and texture to scallions, and are a great substitute for scallions in raw dishes. Scallions taste like onions with a hint of garlic. They’re not quite as crunchy as scallions, but in salads and as a garnish, they work wonderfully. You can also easily grow them in your own garden or in a porch box with your other herbs. 
Ramps are commonly called wild leeks. They are a popular foraging vegetable and are known as a sign of spring, as they are one of the first plants to flourish. As their growing season is so short, if you don’t get ramps when you can, they will be hard to find. However, they are a great substitute for scallions because they look like a slightly smaller version, and can be prepared in all the same ways. They are slightly more garlic in taste than scallions, with less of an onion edge. Because of this, they might not work in salads but are excellent in cooked recipes like soups or potato-based dishes.
Shallots are often mistaken for garlic because the bulbs have multiple clusters, but shallots have brown skin and taste much more like onions. They are sweeter than scallions but provide the necessary bite to recipes. However, they work much better when cooked into dishes, rather than raw. They are delicate in texture, and softer than onions, but when minced finely, they will substitute for scallions very well.
Most people are familiar with garlic bulbs, but garlic scapes are the delicately flavored green shoots at the top of a garlic plant. These scapes have a very mild, refreshing garlic flavor, but they do not stand up to the heat of cooking very well. If using them in heat, stick to a quick sauté or stir-fry.