There are numerous synonyms for the phrase "fellow traveller," each with its own connotations and associations. Some alternatives include "comrade," which often implies a shared political or social outlook, "ally," which suggests a shared goal or objective, and "accomplice," which connotes a more illicit or morally dubious relationship. Other synonyms include "colleague," which suggests a professional or work-related connection, "confederate," which evokes a sense of conspiratorial collaboration, and "associate," which implies a general connection or relationship. Depending on the context and tone, any of these synonyms could be used to describe a person who shares in another's journey or cause.