If all you mean by "housing" is a foam cover for it, just buy a cheap pair of headphones and take the foam covers off of them. If you instead mean that you need something that the speaker sits in and that the foam cover attaches to the front of, how about a plastic food container(salad dressing bottle, etc.) lid? You could hot glue or epoxy an o-ring to the open end of it to create a lip for the foam cover to grip onto, or just hot glue the foam on around the perimeter.