MH to HPS conversion bulb using MH ballast???

is there a bulb that uses a MH ballast and converts it to be a HPS so u can flower with it?

I use the Plantmax 360w HPS conversion bulbs in my 400w MH ballasts. They work great. Some of the cheapest bulbs around, I found them for $20 somewhere but the link is bookmarked at home!

i have the same thing a 400w mh now for my veg then a 360w hps for flower using the same ballast going to switch to flower next week once they have hit 60 days veg . i also use two 90w led tri band ufos for veg and will use them in flower as well .

check 1000bulbs.com I've got 2 from them. kinda high priced.