How to keep flies away from bunny's cage?

i was told to clean my rabbits cage every week. she's an indoor rabbit and we've had her for like 2 years now. every summer, we get flies in our house and they lay eggs in my bunny's feces. no matter how many times i clean it, there's ALWAYS a lot of maggots when i do. i really dont want to start cleaning it every other day or even every day and i was wondering if there was something that keeps the flies away like a spray that's safe on my bunny.