I honestly think they're non-existent due to the fact that they don't want you entering the event and adding to your stack via chips from your pockets or elsewhere.
This is from another forum....I googled it...whether it's true or not, I'd have to believe it. "and The companies making those chips only deal with casinos
and Harrah's can't sell chips with their name on them for legal reasons." The chips also state on them: "NO CASH VALUE"
The Ebay ones are probably a very, Very cheap knock-off. If you're looking for inexpensive wsop chips they won't be authentic because they are expensive make b/c they aren't imported, at least that's what I've read.
I've seen them in a plastic encasing sold as expensive card protectors though.