I don't have exactly what you are describing, but I've been doing a lot of PCBoard layouts for things that include USB to serial converters and microcontrollers. My most recent task is an electronic selector magnet driver (meaning it doesn't have a high voltage loop per se, but instead uses lower voltages (and small limiting resistors) to get the magnetic flux up to full value in a couple of milliseconds).
If Greenkers were willing to come up with a set of requirements (fewer is better than more) I think I should be able to come up with a simple PC Board that functions as a USB to HV Loop interface with ASCII to BAUDOT conversion included. PC Boards fabricated in China are surprisingly inexpensive.
Paul, ad7i