In that case: Spectators don't care if I am showing them a card with a note taped to the back of it. They don't care that I would use an eraser instead of a poker chip or that I have a card case instead of a wallet. They wouldn't care if I had written the prediction across my beefy pectorals. They love the effect.
...and I derived it from the original idea I read in a book that was full of other great effects. Books are nice that way.
If it's all about the spectators, why do you need someone else's props?
I don't mean to spoil the fun you had by buying this trick but I do wish to heal you of CUPS.... or at least give you more bang for your buck. Do you really need to present this specific version of this effect? Especially if your spectators will be astounded either way? You can't truthfully say you're paying the inventor of a secret, because he stole it from the wealth of magic principles available in the world.
Perhaps I should just keep quiet and sell one good old trick at a time for 60 dollars/pounds each. It seems to work quite well. Next time you feel like spending money, let me know and I'll help relieve you.