Not really.
Internet, gun shows, gun shop.
BLue Book of Gun Values
try: gunparts.com gunsnparts.com gun-parts.com
Try local gun shops, gun shows, want ads, e-gunparts.com
Try gun shows, want ads, e-gunparts.com
10-50 USD or so
gun shop, gun show, egunparts, want ad, for sale ad, estate sale, garage sale
No, It is a type of gun
The smallest, best known centerfire handgun round is the .25 caliber (or 6.35mm). The practicality of the .25cal is questionable: you have all of the costs of a centerfire round, with not much more energy than a .22LR rimfire. In fact, nowadays, you are much more likely to find .22LR pistols than a .25cal. One step up from the .25cal is the .32 caliber. This is just about as out-dated as the .25cal, but there were some very popular weapons in .32 caliber, the Walther PPK (James Bond's weapon of choice) is said to be a .32cal (not a .380ACP). There are also pistols made to shoot rifle (long gun) rounds. These tend to be smaller caliber than a .25 cal, but are fairly modern (like a pistol designed to fire .17cal HMR).
The pistol does not have a permanently attached stock- and it is a lot harder to control. The pistol is one handed, the gun two.
Titan brand .25 caliber handguns were made by Tanfoglio, an Italian gunmaker. They use proprietary magazines. Some other .25 caliber magazines from similar handguns may fit, but there is no recognized interchange and no guarantee that a mag that fits will feed correctly. Your best bet is to look for a Titan/Tanfoglio mag at a gun show or a used gun parts dealer like Numrich.
It all depends what your first one is and the quality of it. If your first Airsoft Gun is a AEG, then you should probably but a decent gas pistol for backup. If you decided to become a sniper and you bought a sniper rifle as your first gun then you should look into small battery powered AEGs such as MP5Ks or MP5s. But overall, a good gas pistol would be an overall upgrade to anyones arsenal.