MG3305

I have a 2016 E400 convertible and my wife uses it on occasion to transport our dogs. We have tried a non-custom rear seat dog cover but the straps that go around the rear headrests are a problem since the headrests go up and down when the top is raised or lowered. The straps have gotten stuck and created issues with the top movement. Can anyone recommend a custom rear seat dog cover that does not have this problem?