There must be a source somewhere but I've never found it. I replace torn boots on tractor ball joints quite often with a section of puncture proof bicycle inner tube held on with stainless steel tie wire, works better than OEM. Tractor ball joints are $150 a pop, makes it more worthwhile. The biggest cause of boot failure is over greasing, two shots is plenty, if the grease comes out from under the boot you've overdone it.