I also searched for the LT8365 but couldn't find a way to buy it as a part.
I can't wait until next year, so It's expensive, but I bought modules (boards). This is up to + or -280V, so I need to make few changes.
https://strawberry-linux.com/catalog/items?code=18365
This shop doesn't have an option to ship to the US, so I got help from a friend in JPN.
Made with double sided bread board. HVPS (LT8365) are on the way from JPN.
I planning to divide it into four and stack these in 2 or 4 layers, but I don't think it will be a size that can be called "portable" but I will try...
I am planing to use Toshiba TTC004B instead of KSC2690A.
Cob is lower than KSC2690A (12PF - 19PF) and better hfe linearity.... and I prefer Toshiba rather than KSC/KSA .
Small board is for +/-15V. Small one on the right is 5/20/30 sec timer board (PIC).
For the electrostatic headphone, please refer the following forum.
https://www.head-fi.org/f/threads/my-diy-electrostatic-headphones.498292/