instead of searching for them online, (which to be honest, defeats the purpose a bit), get a field recorder and do it yourself. It's way more satisfying and educational. Will be the best $200 you've spent in a while.
I can only recommend this aswell. I don't record that much myself, but whenever I feel like it could be interesting I just turn my zoom on and do something like crumble an empty chips bag next to it, put it on a clap and see what happens.
Having a good microphone, and a good recorder, is required and expensive.
Better yet.. if you can't afford a recorder, use your phone.