How to stop a feral cat from spraying my basement windows?

this spring, we have a huge problem with a neighbourhood feral cat that keeps spraying our basement windows. We don't have the sunken windows, they are level with the ground. it makes our entire home REEK of cat spray, and it's absolutely horrible. we have tried cayenne pepper, spraying vinegar, orange spray...nothing works, and it's gotten to the point that i am going to loose my mind. what can we do to stop this cat from spraying our windows? our humane society won't trap/take it. we would have to pay a hefty fee to get someone to trap it, and even then, who's to say we won't catch a possum or a racoon in the trap, and then need to pay for that? is there anything we can spray/sprinkle that will discourage this cat from doing this? i don't want my house to smell like a litter box anymore. PLEASE HELP!!!! and no...i won't kill it, so don't suggest that.