Well… I don’t know if there are any apps like that out there but I would recommend making some of your system icons a little smaller, like changing the fast user switching icon, changing the battery icon, and removing some of the menu bar apps that you don’t use all the time, or enable their dock icons. I will look for an app, however. Unfortunately, though, I think the only solution for you is to change the size of the icons you can and remove some.