It is not a replica, but an actual on-screen prop.
I purchased one of the coconut mai tai cups seen in episode 4.12,
There's No Place Like Home - Part I,
during Hurley's birthday party. Below are a few screen captures from the episode.
The cup and certificate were delivered Thursday, June 10, 2010!
I ordered a small display case intended for miniature football helmets
to display cup. It is perfect!