There has only ever been one MRI designed electrostatic that I know of, the Koss ESP900 which is just a 950 with a closed housing. I've heard that HE60's were used for this but never seen anything in the flesh, plus the HE60 headband is magnetic (plus the screws) so something had to be done about that.
The MRI's I've been in all had sound pipes for the audio, simple tubes with the transducers elsewhere and sounded terrible.
The Voce and the Hifiman units were indeed unfortunate. The Voce is well built but sounds like crap (electrostatics are all about that vague sound and loose, uncontrolled bass... ) plus that stupid case they insisted on shipping with them. Now the Hifiman Shangr-la jr. sounded good but that build quality and silly price makes it a solid miss.