I do not have the GPS coordinates but I can give directions to it.
HOURS: Sun, Mon, and Fri 0700-1400
Take the Corso malta exit from the Tangenziale. Go through the tollbooth and stay on the street. Go straight. NOT over the overpass. (If you end up on the overpass, don't panic. Take the first exit, then take the first right, then the first left-the jail will be in front of you. Turn right, and then continue with the directions.) Bear to the right following the sign which says "Via Poggioreale." This sign will be right AFTER the white sign that has Carlo III on it. (Do NOT go through the tunnel. Be sure to get on the surface road) Drive for about 2 blocks on the road until you come to the traffic light. You will see the prison in front of you on the left corner. Make a left here onto Via Nuovo Poggioreale. Drive for some distance down the street (about a mile), and under the highway bridge. Take the first right turn, Via Marino di Caramanico. The market entrance is on the right, about 1/4 mile down the street. Follow the crowds to the market!