When searching for synonyms for "alternative to none," a few options come to mind. One possibility is "substitute," which can refer to something that can replace or stand in for another item. Another option is "option," which denotes a choice among different alternatives. "Choice" and "selection" also convey the idea of having different options to choose from. Finally, "replacement" can refer to something that takes the place of something else that is missing or no longer available. Depending on the context, any of these synonyms could serve as an appropriate alternative to the absence of something.