Opara has also played for Cambridge and Colchester. An offer has been made and accepted by Grays, and now Swindon are waiting for the player to agree terms.
Meanwhile ex Cheltenham Town goal keeper Steve Book should be joining Swindon on trial over the summer as a possible replacement for Bart Griemink who has now left Swindon.
34 year old Book was Cheltenham regular 'keeper until this season, when he was released.