buschur was selling 7cm housings for $140 awhile back, not sure if it was a special...try calling fp, slowboy...but I'd say stick with the 10cm and spend the money. You're probably not gonna find a "dirt cheap" 7cm, and definately not gonna find an 8cm...

edit: or if you don't want to spend money just trade/sell the turbo to a newb and buy a used 16g which are a dime a dozen now.