Synonyms for Fellow traveler:

n.

commuter, dude, business traveler, backpacker, bird of passage, explorer, coach party, caravan, camp follower. bolshevik, commie, the HUAC, the labor movement, communist, the House Un-American Activities Committee, the ANC. fellow traveler (noun)
fellow traveller, companion.
person (noun)
fellow traveller.
somebody on same journey (noun)
companion.

Other synonyms:

bolshevik, commie, the HUAC, the labor movement, communist, the House Un-American Activities Committee, the ANC. Other relevant words:
communist, commie.