You can start with one if that's what you'd like to do, there are probably "fashion" corsets that have the same seam setup. You could also use the duct tape method of creating a pattern or draft it on paper. Whatever you're comfortable with.
Disclaimer : This post written by a Grumpy Old Man
Actually in the pipes:
- Remaking Ser Loras doublet.
- Luke Skywalker, A New Hope
- Wind Waker starter costume in swim material
Eventually: Paul from Dune, Faramir, Harry Sullivan