Go on eBay, they have some great deals. Get yourself a newer ballast. Old ones are magnetic. The new ones are electronic or digital, uses 20% less power also produce less heat. Also get one that is switchable from 220 to 110. Makes it easier to sell if you decide to get rid of it. Buy the whole package together. It doesn't make sense to piece it together. You can buy a cheap 400w HPS with a ballast for under a $100. HTGsupply has one for under a $100. But I would go with a decent electronic not a magnetic ballast.