Thanks for the responses. To recap, it sounds like RA-4 is all there is in terms of a "commercially supported" process. I didn't mean to strike any nerves with Ilfo/Ciba. With some further reading, I discovered that Kodak had a positive print paper at one time (Type 1993 or RD-14). I couldn't find any information on a Unicolor (Type B or RB) process.

The three-color gum and carbon processes interest me. I also discovered that two- and three-color cyanotypes are possible although you're limited to tones achievable by bleaching and toning. Unfortunately (for me) most of the tutorials I'm finding are hybrid in that they rely on Photoshop to produce the registration negatives. So more research and exploring are in order...