@TonsofPuppies, TLDR, PKHex does not detect PCJP 2003 (5th anniv) eggs properly. Here is a link to all of the public ones that are legal (probably legitly acquired back in 2003): Legal 5th Anniv Eggs
While it is possible to create a method to generate the eggs, we find no reason to make this method public or easily available for several reasons:
1) It encourages selling on ebay and etsy, and scamming via trade channels, both of which we do not condone.
2) There aren't that many good IV spreads, and none of these old events make good competitive pokemon anyways.
3) We have so many of them in our collection, that you can just use one of those.
As for academic research and people interested in reverse engineering, the thread @ajxpk linked to has enough info. You can also contact me for help if stuck.