I think I remember seeing a butt stock that someone attached to a Ruger, but it may have been another auto.
I have seen cage style scope mount rails for the earlier P Series with the metal frames.
Sportsman's Guide had longer barrels for the P85 and P89. Longer by a half inch with a compensator port in the top of it to counter recoil. They didn't fit.
Not sure how they would get an auto to cycle with the weight of a long enough barrel to make it a carbine, and the weight of a slide long enough to support that barrel.
Different types of firearms would be for use in different situations. A hand gun seems best suited for a confrontation with a small number at close range. A rifle for confrontation farther away. An actual carbine would be well suited for larger numbers of opponents in an urban environment where wielding a rifle would be an issue. The current "civil unrest" might justify something like this.
After my earlier reply, I came across some kits for popular larger frame pistols. The one that sticks out was called a "Micro Roni". The pistol clamps inside a cage with a forearm strap (thinly camouflaged butt stock), fore grip, and lots of speed holes to make it look cool. It appears to fire through a faux barrel that is suspended in front of the assembly. The appearance of the kits they offer for the various different handgun models appear identical, so their product is basically a cover, with different attachment clamps for different pistols. Attaching one to a P95 would involve making new brackets to clamp to the trigger guard and probably the rail.
You pick up more stability with shoulder fire and a fore grip. But the barrel is the same length, so it still has very limited range. It's a toy to show off at the shooting range, like a 30 round magazine in a handgun.
I had seen the Ruger PC Charger Pistol while researching previously, and had gone right past it. Yesterday a photo showing the pic rail for a butt stock caught my eye. I am trying to attach an MCX butt stock to a rifle, so the pic rail stood out. My understanding is that you couldn't legally attach a butt stock to a PC Charger Pistol, without a lot of fees and government paperwork. Same thing with attaching a barrel that is between the pistol and rifle length, to turn it into a much more serious carbine. (The website for the Micro Roni kits appears to have the same disclaimer on fees and paperwork.) But the PC Charger Pistol at least has the basic ingredients of an actual carbine, because it is a cut-down carbine rifle.
I think the PC Charger Pistol would be a better solution than a kit that attaches a cage over a pistol. All the futuristic military styling, and built more rugged.