Acucut(sp) will create custom Die patterns. The cost was very reasonable and they are great to work with. You can get used die presses for pretty cheap.
I was working with them on making a double 5x7 die to cut 8x10 down. I never had any luck with a high end cutter because of the film base being thick and the film shifting just too much. The project Never came to fruition because I had a serious attack of lackofundacitus after our car broke down. Even then they were very understanding.