I don't think you could fabricate the parts necessary to ignite a HPS bulb, if you could, it certainly wouldn't be safe.. You need a ballast, a capacitor and an ignitor, you can get bare bones kits from here: High Pressure Sodium Ballasts, HPS Ballasts 150watt ballasts are about $50
Or, you could get a completely assembled 150 watt hps ballast, mount, reflector and bulb for $70 (plus S&H) from here: High Tech Garden Supply