Just to answer the original question anyway; as far as I'm aware only items sold by Amazon are eligible for the "global" shipping option where Amazon pre-pays the customs fees.
Think the only option with marketplace sellers that are fulfilled by Amazon is "International Express" which is just as pricey and doesn't cover import fees, so it's a bit of a lottery if you get caught. You're more likely to get caught as well as the package is tracked. I've used it a couple of times when Amazon hasn't stocked what I'm after.