Help with hover flies

Please disregard if not allowed as I am not the owner of these chickens, they are our neighbors.

Their coop backs up to our patio which we use year round as it is covered. It is to the point where we have hundreds of flies in our patio every time we go out. The occasions I have gone to discuss this with them the flies are even more prolific on their property. Our lots are in the city and small (sub 10k sq ft). Other neighbors up to a block away have also mentioned the fly issue in passing not knowing there is a coop in proximity. The last time I discussed this issue I offered to help financially to quell the problem.

What would people recommend to purchase to help this issue? We had hoped last summer with the heat that the flies would not be able to breed in the chicken waste but unfortunately it did not get warm enough to dry out the poop in their coop or they weren't cleaning up regularly. Who knows.

I want to be neighborly and help with this problem but I am unsure of where to start. Last we left it they were going "to do some research" but I simply can't live like this anymore and need to take action at least on our property if they aren't going to do anything with theirs. Any advice is greatly appreciated.