If you have a golf ball the exact size you want, you can use it to make a mold from. Then you can cast the stopper part in clay and attach it to the golf ball and make a mold of that if you want to cast both as one piece. I'd suggest using one of the liquid Tin Cure silicones like Quick Set, the High Strength series, or Amazing Mold Rubber as they aren't very picky about what material they cure against. For the size you want, the liquid mold materials would be a better bet in picking up all those smaller details.
I've worked with Clears in HS-3 molds before and Brian's right - the mold might have been a little colder the second time around. Carol (one of the Alumilite techs) let us in on one of the tricks they use for trade shows - they use a regular household griddle (be sure to never use it for food and keep it ONLY for this) to warm up the molds and leave the molds with the poured resin on it while it's curing. If you don't have a griddle, just zap the mold in the microwave for a minute and it's good to go. Just be sure to keep it in an area that is close to 70 degrees while it's curing and that will help it stay clear too. And if your working area can be close to that temp also, then that's just another layer of protection to help it cure clear.
Other than the foggy look, they came out looking great. I'm not sure if there is a way to fix the foggy look though so you might want to keep that one.