I can't help much. The Mavis Beacon Teaches Typing manual lists some sources for Apple II and Tandy 100, but the only one I could reach by phone no longer has a Dvorak product. Here are the other addresses if you want to risk a stamp:
Dvorak International's information on Keytime (Tel: 206-522-TYPE) mentions software for the PC4 computer, whatever that is!
If you know a current address for any of these products, or any other product for Dvorak users, please send E-mail.
Back to Introducing the Dvorak Keyboard.