Rubber Surgical Tubing
I have solved this same problem with silicone rubber surgical tubing. You can get it at some hardware stores and, of course medical supply houses. Take your pump head and get a size with the appropriate inside diameter. In my case, my LBS stocked the stuff for just this purpose. You just cover each prong on the pump head and cut it off. I does a much better job of protecting the frame than the original Silca parts. Mine has lasted over ten years and shows no signs of needing to be replaced. If you buy a foot you will have a lifetime supply.