For that specific application (cane, not crutch, fortunately), I have found the saw on my Leatherman Wave perfect - it produced a very nice cane effortlessly and quickly. But the Wave is heavy. You can find very nice light saws (2 oz range) at any good home products store.

My best impromptu hiking staff was a mop handle I found, washed up on the beach. It was in a situation where I really needed one, too. Just had to scrape off a little tar and it was good to go. Used it for several years...