How can I fix hollow rubber soled boots?

I bought some lovely black leather boots in Jones last year, but they have grey rubber (crepe?) wedge soles/heels and have worn through at the heel allowing wet to get in as well as small stones which subsequently rattle when I walk! I would love to be able to repair them as apart from this problem they have plenty of life left in them and were not cheap to buy. I would be grateful for any hints or ideas on bow to fix them.