dwarren is correct. The SR series pistols are not even listed in the Ruger catalog now.
I bought two new SR9 pistols late last year when they were still available as distributor specials. Paid $300 from CDNN and $250 from Sportsman’s Warehouse. They sold their SR45s pretty quickly at those giveaway prices too.
Just keep watching to see if & whenever a new run pops up, or try Gunbroker.
I had an early production SR45, but gifted it to one of my sons two years ago. Nice, soft shooting .45.
Your best bet at this point will likely be gunbroker (saw a couple on there earlier today) or similar sites. If I recall correctly, Ruger has "sunset" the line (SR9, SR40, and SR45) and is no longer manufacturing them.
Vance only has the compact left. They said they will have more in soon from inventory but that was last week. Nothing in full size yet this week. The SR series are a good auto when you can find them. Nothing on the internet either in SR45 full size. We have been looking with no luck as well. We have the .9mm versions of the SR and love them for home/property defense with the PCC9. Good luck.