If you can't/don't have the means to sew, I think your best bet would be to search an online store to see if you can get a dress in that colour, and possibly hunt for a corset for the middle part, although corsets can get expensive.
I'm a huge sewer, so of course my advice would be to have someone who can sew help you to oversee a pattern that you think looks similar (Simplicity and Butterick tend to be easy patterns, avoid Vogue like the plague) and take a crack at it. Looking at her dress, I don't think that's something you'd be able to find and to make it accurate would require making modifications to it (i.e. external corset perhaps). You also always have the option of commissioning someone to it

Same as "finding" the dress, but it'd be a lot more accurate.