Cleaning a Retainer?

I have recently had my braces removed. I have 2 retainers I have to wear every night. The only retainer cleaner I have ever used is from Aquafresh. They are denture tablets, you soak them in a tablet and hot water. The thing is I can rarely find this product. Does anyone know of another way to clean your retainers? Soap and water is a no-no.