Keltec, Rorbaugh, Ruger, and Kahr all make such guns. The prices vary from $350 to $900, retail. The keltecs can be had for $200, in good used condition, from private buyers. with a good Kydex pocket holster, with Velcro to keep it in the pocket, and a "hand on gun" start, you really can "beat the drop" of a man having a pistol pointed at you.
You have to know how to sidestep swiftly as you draw, but it can be learned rather easily, using AirSoft guns. It's not too hard to learn to toss up a couple of soda cans with your "weak-side" hand, with the gun hand in the pocket, draw and hit both cans in midair. Try that with any sort of concealed belt rig, and you will see how much faster the (discrete) hand in pocket start position really is! 
The best factory load for such short barrels is CorBon's 100 gr PowRBall jhp, it gets well over 1300 fps in 3" barrels, so it will penetrate clothing and still have enough velocity to "flush out" the clothing debris from the hp cavity and still expand well in the man's chest. That load jumps around a bit in the 13 oz Keltec, but so do any other full power 9mm loads. At the sub 10 ft ranges that nearly all justifiable civilian shootings occur, tho, a skilled man can do fine with such a combo of load and gun. The plastic rig makes the "bulge" in your front pants pocket look exactly like that of a wallet.
For the price of a used glock (at a store) you can have a pair of used Keltec PF-9's, one to ccw and one to practice with. So the fouling and wear of practice does not fall upon the "duty" gun, you see.
The best factory load for such short barrels is CorBon's 100 gr PowRBall jhp, it gets well over 1300 fps in 3" barrels, so it will penetrate clothing and still have enough velocity to "flush out" the clothing debris from the hp cavity and still expand well in the man's chest. That load jumps around a bit in the 13 oz Keltec, but so do any other full power 9mm loads. At the sub 10 ft ranges that nearly all justifiable civilian shootings occur, tho, a skilled man can do fine with such a combo of load and gun. The plastic rig makes the "bulge" in your front pants pocket look exactly like that of a wallet.
For the price of a used glock (at a store) you can have a pair of used Keltec PF-9's, one to ccw and one to practice with. So the fouling and wear of practice does not fall upon the "duty" gun, you see.