high-voltage regulated dual power supply

Does anyone know a design for a regulated power supply that can output +-350V? A simple emitter follower (using 2SC3675) and a couple of zeners create the +350V part without much pain, but -350V is killing me. Are there any PNP transistors in production that can sustain around 450-500V and a few hundred milliamps? 2SA1126, 2SA1193, or 2SA1968 could probably do the job but I cannot seem to find them anywhere.

This power supply is required for an electrostatic headphone amplifier ( http://headwize.com/projects/showproj.php?file=gilmore2_prj.htm ). I use unregulated (and severely underrated because I couldn't find a decent transformer on a short notice) PS right now but it produces only +-270V and is rather noisy...