Seriously dude, the majority of people do have CS:S from what I’ve heard so you are in the minority bitching about something most people don’t need to worry about. That being said, I know how annoying it is because I did not have CS:S when I first bought Garry’s Mod and I know how annoying it is to find random fucking materials and models and textures and shit missing.
I do have one suggestion, and I can personally vouch this works. Go onto a forum, and just ask for $20 (in little donations perhaps) to be e-mailed to your paypal. I got $20 on 4chan one night because I posted a thread asking for donations to do just that, buy CS:S. Honest to god, if you’re too cheap to buy it yourself, ask for it on the internet. I’ll personally donate $5 to you if you can get the rest of the money, I don’t want my $5 not being used.