You will probably have to order custom sized covers to fit your radiators. I suggest a metal cover with small openings to keep out little fingers. The cover will become warm but not hot enough to burn. Here is a picture of a basic cover.

Here is the link for website where I got the picture where you can order the specific size and color. There are several others on line.

Where are you located? There may be a local shop who can make them for you and avoid the cost of having to shipping a dozen covers.