Well, I'd never barter for something as storage sensative as insulin. In that case, I'd recommend evac.

But I stash a few packs of cigs in my gear. I haven't smoked in years, but other people can't shake the habit. I don't plan on getting much for them, but someone holding gas might be willing to swap a couple gallons for a pack of butts after a week without. Nic-fits suck!