http://www.fpsbanana.com/guis/download/3942That is the site, just hit download. Here is how to install them.
1. If you end up with a scope_lens.vtf when you download a scope, extract it to "...\counter-strike source\cstrike\materials\overlays\"
2. If you just have a materials folder, drag and drop the materials folder onto the background of the cstrike folder. (...\counter-strike source\cstrike\)
3. The material file is located in cstrike\materials\overlays\scope_lens.vtf