Bob, I think I have seen 6, maybe 7, SSP-91's in real life at shows and gun stores. Stainless steel examples are even scarcer, never seen one in the flesh. I own 2 of them, they aren't common. I acquired my first, a .308, in 1993 or 94, the second, the 7mmBR, came in 2017. SSP's usually are found in heavier chamberings and aren't much for extended range sessions with old wrists, a .223 would be great.
If you would like to own one, try Gunbroker. They show up now and then, frequently over priced for an orphan gun like these.