I had mice in my car until I stopped composting kitchen scraps and hung a bag of snake sheds in the car. It's worth a try. You might be able to get sheds from a pet shop. I got mine from a friend who breeds rattlesnakes. Good luck finding those tiny holes!
I live in a boreal forest, so there are mice everywhere. No amount of deterrent works, unfortunately.
I live in a redwood forest/oak bay woodland/chaparral interface. Lots of mice. Fortunately, also bobcats, coyotes, and foxes to hunt mice. Birds also use snake sheds in their nests seemingly to deter small mammals. www.allaboutbirds.org/news/why-bir...
It sounds like the snake sheds would likely work best in an enclosed space such as a small car (like mine), closet, or the space under a sink.
Thanks for the suggestions, though I don’t think it will work for me. We also have lots of things that eat the mice, but not enough to keep them out of my house if there is still a hole.
Good luck finding the gaps!