Shorter way to say "conversational partner"
With regard to "interlocutor," it's the generic English term for "the person with whom I am speaking." Anything else is likely to be a nonce coinage, like, "conversant," or "discussant."
try dialoguer
dia·loguer n. Usage Note: In recent years the verb sense of dialogue meaning "to engage in an informal exchange of views" has been revived, particularly with reference to communication between parties in institutional or political contexts.