You need to download GFCscape, go to steam > steamapps > counter-strike source shared.
after you double click that, you go cstrike > materials > models > whatever
its the same thing as having all the default skin files visible in your cstrike folder, but since they arent normally, you have to use GFCscape to get them. pm me if you need more help
At that link you requested where to get the skin file. Well I'll tell you XD
First, Download GFCScape: http://nemesis.thewavelength.net/index.php?p=26
Then your going to want to locate your steam folder, steam apps, and find counterstrike-source shared. Navigate to materials, then models, weapons, v_models, and pist_elite. Your going to need to get VTFEdit so you can view the files. google it, I cant find it sorry =\. Then open the pist_elite.vtf file in GCFScape and then itll open in VTFEdit. Go to file, export, and export it to your desktop. Open it in photoshop, and your good to go! =]]]]]]. Msg me if it was too confusing, I kind of wrote it fast because Im skinning my knife