You could try here:
Annual Holiday Insurance - Ski Insurance - Backpackers Insurance
It's the "Adventure Travel" section that may help.
I was amused the other day when I was getting a re-quote for Life Cover for my mortgage as I was asked if I engaged in any dangerous hobbies/pastimes like bungie jumping/skydiving etc. I said No! Just Archery. The chap on the phone was quite serious when he said that Archery wasn't considered dangerous as it would be very difficult to shoot yourself. Its just dangerous for the people around you.
I said, you were not there last summer when the bow string came off as I drew back and I thought I had shot myself... the arrow did swing back and knock my hat off.
Hey, would that qualify me for the Fonz Award thing?