I think they are used to keep the ears tidy or dry
I have never needed to use them, I think they look a bit silly
, but I suppose they would be useful for traveling if your cocker drooled excessively as some can do. A friend of mine puts a snood on her cocker before it eats to stop the ears dangling in the food.
You could make one yourself with a piece of material and some elastic. Or you could try Hub International.
Tracey