Most cities animal control will lend or rent a live trap. When you catch a cat, you take it and the trap to animal control/pound. You take the trap home and bait it again.
We had a problem with a flower bed under a deck. Cats found the dry dirt a great potty. Trying to plant flowers you would get your fingers in a fresh loaf. There was so much urine in there that the flowers did not grow well. In a month we trapped 30 cats. One owner went to court. The bylaw officer stated he probably wanted to know which neighbor had trapped his cat and that he would likely go pay the fine once he knew. Sure enough, he paid the fine and came over to complain to us. Said one neighbors old cat had been euthanized and the owners just thought it had been run over. Well I have never tollerated BS or bullies. Thus I calmly explained that that would not have happened if the cat was in their yard like bylaws stated. When the guy left the bylaw officer said he could not believe I stayed so calm. I had noticed he was even getting annoyed at the guy.
We had a dog and no license for her. Another officer came to our house soon after to ask if we had a dog and a license. I calmly replied I would be happy to do that only when the city required licensing cats. Never heard back on that.
The city mayor was a woman cat owner who had introduced the law requiring dogs to be licensed. She felt she had done a wonderful thing to clean up the unsightly mess of dog land mines. At least dog landmines are visible so you can avoid stepping on them.
Does not solve the odour problem which is similar to that of mice intrusion, but may solve the cat problem.