KWC Smith and Wesson Airsoft?

Okay I recently purchased this gun from ***** Sporting Goods and I was wondering where I can find a high capacity mag for it. Heres a link to the same gun on shorty usa http://www.shortyusa.com/airsoft.html?a href="http://www.shortyusa.com/cart/viewitem.html?II=1570&UID=1230509606-72.186.199.42&CA=&RID=" rel="nofollow"http://www.shortyusa.com/cart/viewitem.h…/a I want one of the magazines that stick out farther than the handle of the gun and hold like a bunch of ammo! I run out way to fast with the stock 15.