Have you used your search engine for, say, 'Ruger Bisley 357 pics'to see what pops? Some of the 'limited edition', like TALO or Lipsey may have, but they can be hard to acquire and/or (sometimes) afford. I seems to me that Ruger prefers to have the 'specialty' companies foot the bill and market the items rather than marketing through the Ruger catalog. It makes sense for a manufacturer and does give us more choices that we may otherwise not have.
If not found, you can make your own, for a price.