Anyone know where I can buy long post stud earrings online?

Hi there, I suggest to buy the earrings you want and go to your local jeweler and ask him to get long posts (just the posts) and replace the old posts with the new ones. Every jewelry findings wholesaler has other post sizes ((up to at least 14mm I believe). It should not be more than $20.- $30.00 for the pieces including the work (14k or 18k).
If you need just the posts you can contact [email protected], they can supply the posts at a minimum cost.

Hope this helps!