Most hardware stores sell HPS and MH BULBS, but you have to remember, an HPS bulb (regardless of how small the wattage) will NOT run off of a standard light socket, even if the mogul bases (bottom screw-in part) is the same size. Even if it's just a 100w HPS bulb. The reason for this is because standard incandescent, halogen, and fluorescent lights operate off of an uninterrupted current that is provided by the power cord via the electrical outlet. But HPS and MH bulbs operate by supercharging compressed gases inside of an arc tube, and actually require an ignitor (as well as several other components) in order to light those gases. So don't waste your money buying an HPS bulb unless you have an HPS ballast to light it up. It won't work without a ballast. That's why I recommended either building one yourself, or ordering one online.

Hate to be the bearer of bad news, but that's a common misconception for low-watt HPS bulbs. Take care, and best of luck in your lighting endeavors. :jointsmile: