Ben Krasnow on Twitter: "You can still buy low pressure sodium lamps (eg on Amazon), but the ballasts are expensive and rare. I found that using a cheap CFL ballast, and replacing
Sola E-SZA00W100 - 100 Watt - 120-277 Volt - HPS Ballast | CityLightsUSA.com
Lighting Comparison: LED vs High Pressure Sodium/Low Pressure Sodium