What does "portable" imply?
The Realiser requires 120V power, so you can't carry it around with you and use it "while running" or "at the gym". There is no "portable" version of the Realiser.
The SR-009 is hardly "ear buds", and it's oiginal wood case is more like luggage if you wanted to travel with it. Would you really check your $5K headphones with your luggage?
The matching Stax headphone amps (e.g. SRM-007tii or SRM-727) are about the same physical size as the headphones that go with them, as is its carton. And again, would you take a chance checking a $2K amp as luggage?
Most importantly is the "open" nature of the SR-009, meaning all outside ambient noise in your listening environment will come right through into what your ears hear. Also, anybody outside your headphones but in the same listening environment with you will hear LOTS of sound, almost as if you were wearing speakers on your head. Use of open electrostatic headphones is not intended for (a) a noisy environment, or (b) an environment with other people around.
So exactly what are your "specs" for portability and its use?