I really like the Star PD .45, it's $300, 25 ozs, 7.5" long. The other "trail pistol" is a Smith 2214, 6" long, 18 ozs, great trigger pull and sights, very accurate. About $250 used. Both are out of production, both can be found on GunBroker.com and GunsAmerica.com. With a total wt of a mere 43 ozs and about the same bulk as a 4" .44, the pair offer lots more versatility.
Why make the noise, waste the cost of a .44 or .45 on a frog, snake, bird, etc, when you can use the 2" at 25 yd accuracy of the Smith .22lr autopistol? Why have nothing more than a .22lr, when you need to stop a dog or a man, or want to take a deer, hog, etc? The .44 is a poor defensive choice, especially for ccw, but the PD .45 is not. Load it with 165 gr Corbon PowRBall ammo and it will be a powerful, yet controlable friend. Why not have the .22lr for some plinking, mud turtale-popping, etc? 2 compact, lightwt, accurate guns make more sense than one big, heavy gun.
I see quite a few favoring a big, heavy .22lr, and nothing else, for "survival" or trail-hiking with a pistol. Sure, maybe you can brain a deer at 20 yds with such, but I know for a fact I can hit the deer in the chest at 40 yds with the Star .45, and I won't have to try to brain attacking dogs or men with it, either. I surely would have to get head hits on such if all I had was a .22lr pistol.
I believe that this pair of guns makes a lot more sense than having just a rifle, or a pistol-carbine combo (in the same caliber). Such a carbine and pistol have the same handicaps. If I am going to lug around a rifle, it's going to offer me something that I can't get with my pistol. As in the 1/4 mile fighting distance of the AR-15 in 223, with its .22lr conversion unit.