150 MH Conversion Bulb

I have a 150 HPS light/ballast that i bought from htg supply. I am looking for a 150MH conversion bulb for this system. Ive heard that i can not use a 150 MH bulb because the ballast wont ignite it therefore I need a conversion bulb. I cant find one so Im hoping someone has some info on this. Plus rep for anybody that can lead me to getting a 150 MH conversion bulb. Thanks

ive only seen conversion bulbs 250 watt and above. post if you find one, i'm interested as well.

Im wanting to grow a bonsai mother plant and figured i couldnt convert my 150hps into a 150MH but i dont think they have a 150MH conversion bulb... hopefully someone knows something.. other wise i guess ill half to do cfls or something else