Are there silicon wireless keyboards for apple machines?
You can purchase a Moshi ClearGuard keyboard protector directly from Apple and use it on your wireless keyboard. I have one in use at home in the kitchen/family room for our AppleTV 3rd gen. Comes in handy when I'm cooking and want to use the keyboard as a remote without having to wash my hands!

BTW/ Silicon is an element (#14 on the Periodic table.) Silicone is a flexible synthetic polymer used for adhesives, lubricants, cook-wear, insulation, and water-proofing.