I'm not exactly sure which valve that is. A picture would help.
If the 1" Irritrol 100 valve pictured below looks like it'll work then you'll either need to buy a whole new valve and harvest parts or buy a retro-fit kit. You wont be able to use your old diaphragm with a new bonnet. They're double beaded now. I'm assuming you mean the top half of the valve from what you've stated in your post