https://www.amazon.com/dp/B01JSYB3UO/ref=cm_sw_r_cp_api_glt_fabc_NAAM8GHVZ7191PGF9G00

These do a great job of attracting and killing flies. The downsides: they smell bad and can maybe bring more flies than you would have without it. Maybe there’s somewhere you can put it that would work well for you.

Also, I just ordered some fly bait spray from domyown.com (https://www.domyown.com/pt-alpine-pressurized-fly-bait-p-12299.html?gclid=CjwKCAjw092IBhAwEiwAxR1lRtOgAHIwjJtcQBpXXvhz-_x3cyJ35AcdMH98xwZw3YheA7yXth6SyRoC_rQQAvD_BwE). Haven’t tried it before so not sure yet if it works well.

I’m not a professional pest controller.