Sorry to hear about your buddy, going to see him (if you can) would mean so much more than any gift, but a piece of surf art would definitely be choice as well
If you go the hand plane route check out the ones Eric Coulson is making down at Surf and Adventure on Sandbridge Rd. He went through the whole cancer thing years ago and is still living strong 14yrs later.
Party Missle Handplanes
an eighth of og kush and a copy of what is really going on/wrong.
if your buddy has a good sense of humor it'll be the best gift ever given