I love my Ra lights, and they're absolutely tanks, so it pains me to say this, but...
Have you considered a 4Sevens QMiNi 123? It's a 1xCR123 extremely small in stature with a fairly straightforward twisty interface.
It's not a Ra, it's not built like a Ra, it's probably nowhere near as durable as a Ra, but it's also nowhere near the size of a Ra and for $40 shipped it's well within most people's budgets to purchase on a whim and try out.
If you're going to start making the Twisty (or Clicky, my chosen poison) smaller you're going to have to use less material, have thinner walls, smaller springs, less circuit board area for programability. In short, you're making a Q MiNi anyway.
I bought the MiNi in AA (I don't have any other AA lights and narrower was more important to me than short), and for the price it's a great light! I still carry my Ra Clicky but my NW MiNi fills a nice niche as a small edc light.
Q MiNi AA
Q MiNi 123