To meet your needs of manual safety in 45ACP, you want a model p-90 (blue) or kp-90 (Stainless Slide)
The P-97 is the other ruger 45 with a polymer frame and is available as a decocker only.
Remember though that Rugers have a trigger safety in that they only go bang when you pull the trigger, If you were cocked in the single action mode and for some reason the hammer dropped without you pulling the trigger, it wont go bang.
I have rugers doecockers and manual safety versions and prefer the decocker. As a matter of fact I started carrying with the manual safety off to resemble my decocker models.
Good accurate, reliable weapons that are a good value. If you purchase through davidsons
www.galleryofguns.com they are gauranteed replaced with new one for life.
But as others have said in above posts, can't cock and lock. First pull is double action unless manually cock hammer with chambered round, all successive rounds are then single action with slide locked open on last round so swith mags, release slide stop and you are ready to go in single action agan.
The first double action pull takes some getting used to with my first shot usually 5 inches lower than the single action group but still in center mass.