Found the dress i want but i can't find where to buy!

I have found my absolute dream dress; however I have looked online to purchase but cannot find it anywhere. I also have researched custom dress makers but they are outrageous on their prices. I need help on how create this dress. I want exact replica with material. There's a little wiggle room on the sash but placement on the dress I don't want to change. Because I have found some similar but the neckline is all wrong or they put more purple on it than what I want. I just need help with obtaining the dress of my dreams for my big day! Thanks