I talked with Shannon over at Thunder Power about that a few weeks back. My best advice ... call the number listed and ask for it. The more folks that do that, the better chance they will still honor it. The chap that originally set that deal up is no longer there. His replacement hopefully will see that these 50mm EDFs are still growing in popularity (1,450,000 hits+ on this review) and that they stand to benefit by honoring the discount.
Please let us know here how it works out if you DO ring them.