You're very right not to buy something off the rack. It won't be cheap (even shite mass produced corsets are pricey) and it won't fit (no matter what body type you have).
You definitely want something bespoke.
You definitely want someone with a great reputation.
And ideally you'll find someone close enough that you can get to their studio/workshop/shop to have at least one fitting.
Oh and don't do your own measurements, when you do your own measurements you have to bend and move your body in ways which skew the measurement. Find someone to help you and then do each measurement 3x (write each time down so you can see how consistent you're being) OR just go to a local seamstress and have them measure you.
I'm rather fond of Stormy Leather's work in San Francisco.
/NOT work safe
http://www.stormyleather.com/subcatm...324&1=325&2=-1
Where ever you decide to go, it will be expensive, and deservedly so - making corsets is REALLY detailed and difficult work.