I definitely love the creativity! A year or so ago I went to a plastics company here in town and asked what it would take to mold some new cases. It was some pretty serious bucks, mostly in setting up the mold/die/whatever they call it. Once you have that it's like $1/case, but you'd have to sell thousands of them just to break even on the die setup.
I decided instead to just buy keith courage and sports titles however many times I needed to in order to have cases for all my games. ;-)