Searched 510s today as rockauto started selling windshields, found they were in stock. Looks like its a good day for 510s.
1970 NISSAN 510 1.6L L4 : Body-Exterior : Windshield Glass Price
VARIOUS MFR Part # FW00204N
4 Door Station Wagon; Type: Windshield; Position: Front (Color: Green Tint)$166.79