The producers in the Nestos Valley are outside the tourism circuit - no TripAdvisor listing, no export to Germany or the US. They sell to local tavernas, to family networks, occasionally to passing drivers. Ask at any kafeneio or petrol station in Stavroupoli, Toxotes, or any small settlement along the Nestos route for a local winery recommendation. The wine will be Thracian PGI or sometimes unlabeled - rough, tannic, local, genuine. This is Greek wine before wine tourism existed: made for the family table, not for the international market. When you find a local producer willing to pour, ask: 'Do you sell outside Greece?' The answer (almost certainly: 'No, just here') is the point.
🔄 BACKUP: If no producer is found, stop at a local taverna and order house wine. Ask where it comes from. The answer will locate the source of the valley's wine economy.