Make your own. Find very small duck figure or head and drill out the bottom and glue a generic cap in it.The dollar store would be a good place to look. :idea:
I made these out of some plastic cake decorations, regular plastic valve caps and Super Glue. I used an X-acto knife to cut the bottom of the cat's legs so that they fit snug on the valve cap. I tightened the valve cap onto the wheel first and then glued the cat on so that it was oriented in the direction I wanted. It's easy...have fun!