If worse comes to worse and you still want to make your head before Halloween you may have to go the hamster ball route. It turned out smooth and I just messed up with my fabric and rushed putting it on so thats why I did not turn out the way I was hoping The slits on my ball at least are not raised so I had no problem fitting the fabric around the head. I reinforced the plastic pieces from where I was cutting with tape before I put the fabric on the head.
Just make sure you cut your mouth with the dremel in a way that does not directly cut into the screws and you will be fine. The hamster ball never lost its integrity. Yes there are metal screws around the equator of the ball but in my mouth I believe cut out a little less than half of the screws and the ball was still holding its shape solidly. I did indeed used a 13 inch hamster ball and I think it worked out fine. Hey I had the same problem with 1000bulbs and trying to find an acrylic globe but I could not find one at a reasonable price.
