Zami,
My understanding (considering placing an order for a 66 and already having an endorsement to fly one) is that the factory are not offering bubble windows, as they do not believe they would offer any benefit.
Owning a 44 with bubble windows, and having flown a 66 for 6 + hours, I agree with the factory. The standard windows are very good already, offering great vision for all.
Cheers
Arrrj