We recently adopted a kitten, I kept an eye on facebook pages that had cats in 'hogares transitorios", where they're basically just in a temporary home with very few animals, we found him here but there are many pages like it:
https://www.facebook.com/adoptar.gatito
I would be careful about protectoras, while it's sad because you want to save the cats from that situation, at the same time they can be dangerous because they sometimes have more cats than regulations allow, and illnesses spread. We adopted from a protectora and our cat died after 5 months because he had a chronic illness he likely got there, it was heartbreaking.